Cylinder In Proximity Research Articles

Numerical investigation on compressible flow around a cylinder in proximity to the heated wall

Numerical investigation on compressible flow around a cylinder in proximity to the heated wall

Spacing Ratio Effects on the Evolution of the Flow Structure of Two Tandem Circular Cylinders in Proximity to a Wall

The flow around two tandem circular cylinders in proximity to a wall is investigated using particle image velocimetry (PIV) for Re = 2 × 103. The spacing ratios L/D are 1, 2, and 5, and the gap ratios G/D are 0.3, 0.6, and 1. The proper orthogonal decomposition (POD) method and λci vortex identification method are used to investigate the evolution of flow structure, and the influences of L/D and G/D on flow physics are shown. At L/D = 2 and G/D = 0.3, a “pairing” process occurs between the wall shear layer and the upstream cylinder’s lower shear layer, resulting in a small separation bubble behind the upstream cylinder. At L/D = 1, the Strouhal number (St) increases with decreasing G/D. At three gap ratios, the St gradually decreases as L/D increases. At G/D = 0.3, there is nearly a 49.98% decrease from St = 0.3295 at L/D = 1 to St = 0.1648 at L/D = 5, which is larger than the reductions in cases of G/D = 0.6 and G/D = 1. The effects of L/D on the evolution of flow structure at G/D = 0.6 are revealed in detail. At L/D = 1, the vortex shedding resembles that of the single cylinder. As L/D increases to 2, a squarish flow structure is formed between two cylinders, and a small secondary vortex is formed due to induction of the lower shear layer of the upstream cylinder. At L/D = 5, there is a vortex merging process between the upper wake vortices of the upstream and downstream cylinders, and the lower wake vortex of the upstream cylinder directly impinges the downstream cylinder. In addition, the shear layers and wake vortices of the upstream cylinder interact with the wake of the downstream cylinder as L/D increases, resulting in reductions in velocity fluctuations, and the production and turbulent diffusion of turbulent kinetic energy are decreased behind the downstream cylinder.

Turbulent wake characteristics for a circular cylinder in proximity to a moving wall

This study investigates the scenario of flow past a circular cylinder in proximity to a moving wall (or equally a body translating in still fluid parallel to a stationary wall). Fifty high-fidelity three-dimensional direct numerical simulations are performed over a parameter space of turbulent Reynolds numbers (Re) of 300 to 1000 combined with gap-to-diameter ratios (G/D) of 0.2 to 3. The flow, hydrodynamic and turbulence characteristics over the (Re, G/D) parameter space are examined in detail. Small-scale rib-like mode B structures and alternate vortex shedding are observed for all cases. The streamwise location for the vortex shedding (quantified by the wake recirculation length Lr) varies strongly with both Re and G/D. The variation of Lr with Re and G/D can be explained by the spanwise circulation $\varGamma_z$ fed into the wake, where the variation trends of Lr and $\varGamma_z$ are inversely correlated. The variations of the mean drag and fluctuating lift coefficients are also governed by the variations in Lr and $\varGamma_z$ . The total kinetic energy in the wake region reduces drastically as G/D reduces below 0.8, which is contributed collectively by (i) reduction in the strength of the shed vortices, (ii) downstream movement of the location of vortex shedding and (iii) associated delayed generation of streamwise vortices. The present results on a moving wall also help to explain several flow and hydrodynamic characteristics reported in the literature for a stationary wall, because the moving wall eliminates the complex wall boundary layer and retains a ‘clean’ near-wall effect.

A pilot study of inflatable penile prosthesis placement in transgender neophallus using Tutoplast® pericardium graft sock technique.

Placement of an inflatable penile prosthesis (IPP) in a transgender patient's neophallus carries unique considerations versus cis-gender IPP placement in mitigating infection, erosion, and overall complication rates. An example of this includes the lack of an anatomical corpus cavernosum and crura for cylinder placement and anchoring. Multiple grafting approaches and materials have been utilized to mitigate possible cylinder instability and improve anchoring. Here we describe our experience and surgical technique in IPP neophallus placement utilizing a single cylinder with distal and proximal cylinder human cadaver pericardium (Tutoplast®, IOP Ophthalmics, Costa Mesa, CA, USA) grafts. Our goals were to determine postoperative satisfaction and device functionality in patients undergoing transgender neophallus IPP placement using our technique. Both patients report satisfaction and no complications at last follow-up (currently up to 14 and 23 months post-operatively, respectively) with satisfactory erectile function and ability to perform penetrative intercourse. In neophallus IPP placement, the anatomical differences compared to cis-gender IPP operations require unique considerations such as cylinder grafting material selection for proximal cylinder fixation and mitigation of device erosion rates. Optimization of grafting material in neophallus IPP placement in an effort to reduce erosion rates has become increasingly important as frequency of this operation increases. Utilizing human cadaver pericardium graft in distal and proximal cylinder coverage shows beneficial preliminary outcomes in our patients.

Numerical study on compressible flow around a circular cylinder in proximity to the wall

In the present study, the compressible flow around a circular cylinder in proximity to the wall is investigated. By using direct numerical simulation approach, the flow behavior with the Reynolds number 100 and the Mach numbers 0.1–0.6 are examined. The numerical result shows that the compressibility effect would enhance the flow stability, whereas the strength of shedding vortices, the shedding frequency, and the fluctuation of aerodynamic force are reduced by increasing the Mach number. Through the examination of signed enstrophy and shear steepness in the cylinder boundary layer, it is found that the vortices shedding from the free-stream side and the wall side are concurrently inhibited by the wall when the cylinder is fully embedded in the wall boundary layer, and the strength of the wall-side vortices is relatively weaker. This imbalance would be intensified when the cylinder gets closer to the wall, and thus a reduction in the shedding frequency is produced. Based on this effect of wall proximity on frequency, the flow behavior is divided into three regimes, i.e., high-frequency, low-frequency, and completely suppression regimes. Finally, from the observation of mean forces, the trend of mean drag and lift force coefficients with regard to the Mach number and gap ratio is described as the scaling behavior in terms of two piecewise functions.

(042) Inflatable Penile Prosthesis Placement In Transgender Neophallus Using Novel Human Cadaver Pericardium (Tutoplast®) Graft Sock Technique

Abstract Introduction Placement of an inflatable penile prosthesis (IPP) in a transgender patient’s neophallus carries unique considerations versus cis-gender IPP in mitigating infection, erosion, and overall complication rates. Traditionally, the IPP implants used in cis-males are also employed in transmasculine patients. However, there are unique challenges in the transmasculine population, with one of the most significant being the lack of anatomical corpus cavernosum and crura for cylinder placement and anchoring. To account for this, multiple grafting approaches and materials have been utilized in IPP neophallus placement with the goal of facilitating cylinder anchoring and stability. Here we detail our experiences using a novel grafting approach with Tutoplast® pericardium graft in a “sock” and “cap” technique in IPP placement in a transgender neophallus. Objective Our objective is to evaluate postoperative satisfaction and device functionality in patients undergoing transgender neophallic IPP placement using our technique. Methods We describe our experience and surgical technique in IPP neophallus placement utilizing a single cylinder with novel distal and proximal cylinder human cadaver pericardium (Tutoplast®) graft. Results We performed neophallus IPP placement with this novel grafting technique, with operative images and graft details shown below. Patients had no complaints post-operatively, with cylinder and pump found to be in good position at first post-operative visit 6 weeks following surgery. There was no difficulty with urinating through the neophallus. All patients report continued satisfaction with device as well as ability to perform penetrative intercourse with device activated. All patients reported satisfaction and no complications at last follow-up (range: 3.5 months to 13 months), with all patients possessing continued satisfactory erectile function. One patient noted occasional mild pain in neophallus that self-resolves and does not cause any concern. Conclusions In neophallus IPP placement, the anatomical differences compared to cis-gender IPP operations require unique considerations such as cylinder grafting material selection for proximal cylinder fixation and mitigation of device erosion rates. Utilizing human cadaver pericardium (Tutoplast®) graft in distal and proximal cylinder coverage shows positive preliminary outcomes in our patients. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Run Wang, MD, FACS is a consultant for Boston Scientific and Teleflex.

(147) Multicenter Evaluation of Inflatable Penile Prosthesis Placement in Men with a History of Priapism

Abstract Introduction Inflatable penile prosthesis (IPP) can be used in both acute and delayed management of priapism-induced erectile dysfunction. Prolonged priapism may result in corporal fibrosis that makes IPP placement more difficult. The current literature on IPP placement in men with a history of priapism is limited to small series and often single-center experiences. Objective We sought to evaluate a multicenter experience of IPP placement in men with a history of priapism. Methods We performed a multicenter, retrospective cohort study of patients with a history of priapism undergoing IPP placement by 7 highly experienced implant surgeons. Malleable prosthesis placement patients were excluded. Demographic, intraoperative, and postoperative variables were collected. Descriptive statistics were performed using mean and standard deviation for continuous variables, whereas frequencies and percentages were used for categorical variables. We evaluated differences in complication rates in those undergoing early or delayed IPP placement. We defined early placement as ≤4 months from priapism to IPP. Results 31 patients underwent IPP placement at a mean of 97.4 ± 26.7 months following ischemic priapism. The mean duration of priapism was 52.3 ± 21.2 hours. The mean age of the cohort was 52.4 ± 4.2 years with a mean follow-up of 11.6 ± 1.3 mo. Overall, 25 patients (48.3%) had a prior shunt for priapism and 6 (19.4%) had penoscrotal decompression. Four patients (12.9%) underwent early placement and 27 (87.1%) delayed placement. Intraoperative urethral injury occurred in 1 (3.2%) patient. Infection occurred in 1 (3.2%) patient at 4 months postoperatively and was explanted without salvage. Seven (22.5%) implants were revised or removed for infectious or non-infectious complications at a mean 8.8 ± 1.0 months after implantation, of which 5 (71.4%) were cylinder-related (2 displacements of a cylinder through the corporotomy, 1 lateral displacement of the distal cylinders requiring revision, 1 proximal cylinder migration, 1 cylinder leak). No complications occurred in those undergoing early IPP placement. Full-sized cylinders (Boston Scientific CX or Coloplast Titan) were used in all cases that resulted in cylinder extrusion or migration. Narrow cylinders (Coloplast Titan NB or Boston Scientific CXR) were used in only 9 (29.1%) cases. Conclusions IPP placement in men with a history of priapism carries a notable incidence of non-infectious complications, especially in men undergoing delayed placement or when full-sized cylinders are used. Few IPPs in this series were placed early after the priapism episode, as our surgeons are predominantly at tertiary referral centers. Priapism patients should be referred to prosthetic experts early to decrease future morbidity. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Antares Pharma: SpeakBoston Scientific, Clarus Therapeutics, Coloplast, Cynosure, Promescent, Sprout, Viome

MP62-01 MULTICENTER EVALUATION OF INFLATABLE PENILE PROSTHESIS (IPP) PLACEMENT IN MEN WITH A HISTORY OF PRIAPISM

You have accessJournal of UrologyCME1 Apr 2023MP62-01 MULTICENTER EVALUATION OF INFLATABLE PENILE PROSTHESIS (IPP) PLACEMENT IN MEN WITH A HISTORY OF PRIAPISM David Barham, Muhammed Hammad, Daniel Swerdloff, Kelli Gross, Georgios Hatzichirstodoulou, James Hotaling, Tung-Chin Hsieh, James Jones, Ian Pearce, Hossein Sadeghi-Nejad, Maxime Sempels, C Austin Service, Jay Simhan, Faysal Yafi, and Martin Gross David BarhamDavid Barham More articles by this author , Muhammed HammadMuhammed Hammad More articles by this author , Daniel SwerdloffDaniel Swerdloff More articles by this author , Kelli GrossKelli Gross More articles by this author , Georgios HatzichirstodoulouGeorgios Hatzichirstodoulou More articles by this author , James HotalingJames Hotaling More articles by this author , Tung-Chin HsiehTung-Chin Hsieh More articles by this author , James JonesJames Jones More articles by this author , Ian PearceIan Pearce More articles by this author , Hossein Sadeghi-NejadHossein Sadeghi-Nejad More articles by this author , Maxime SempelsMaxime Sempels More articles by this author , C Austin ServiceC Austin Service More articles by this author , Jay SimhanJay Simhan More articles by this author , Faysal YafiFaysal Yafi More articles by this author , and Martin GrossMartin Gross More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003320.01AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Prolonged priapism can result in corporal fibrosis which may make IPP placement more difficult. The current literature on IPP placement in men with a history of priapism is limited to small and often single-center experiences. We sought to evaluate a multicenter experience of IPP placement in men with a history of priapism. METHODS: We performed a multicenter, retrospective cohort study of patients with a history of priapism undergoing IPP placement by 9 experienced implant surgeons. We excluded patients who underwent IPP in the acute priapism event. Demographic, intraoperative, and postoperative variables were collected. Descriptive statistics were performed using mean and standard deviation for continuous variables, whereas frequencies and percentages were used for categorical variables. We evaluated differences in complication rates in those undergoing early or delayed IPP placement. We defined early placement as ≤4 months from priapism to IPP. RESULTS: 53 patients underwent IPP placement at a median of 29.5 months following ischemic priapism. The mean duration of priapism was 42.6±14.1 hours. The mean age of the cohort was 51.5±1.4 years with a mean follow-up of 16.4±9.5 mo. Overall, 19 patients (36%) had a prior shunt for priapism and 7 (13%) had penoscrotal decompression. Only 5 (9%) patients underwent early placement (≤4 mo) whereas 48 (91%) underwent late placement. No complications occurred in those undergoing early IPP placement. Complications occurred in 19 (39%) of patients undergoing delayed placement. Intraoperative urethral injury and proximal perforation occurred in 1 patient each. Infection occurred in 3 (6%) men. Postoperative complications occurred in 17 (35%). Cylinder related complications accounted for 8 (47%) (3 displacements of a cylinder through the corporotomy, 1 lateral displacement of the distal cylinders requiring revision, 2 proximal cylinder migration, 2 cylinder leaks). Fifteen (22.5%) implants were revised or removed for infectious or non-infectious complications. Full-sized cylinders were used in all cases that resulted in cylinder related complications. CONCLUSIONS: IPP placement in men with a history of priapism carries a notable incidence of complications, especially in men undergoing delayed placement or when full-sized cylinders are used. Few IPPs in this series were placed early after the priapism episode, as our surgeons are predominantly tertiary referral centers. Priapism patients should be referred to prosthetic experts early to decrease future morbidity. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e861 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information David Barham More articles by this author Muhammed Hammad More articles by this author Daniel Swerdloff More articles by this author Kelli Gross More articles by this author Georgios Hatzichirstodoulou More articles by this author James Hotaling More articles by this author Tung-Chin Hsieh More articles by this author James Jones More articles by this author Ian Pearce More articles by this author Hossein Sadeghi-Nejad More articles by this author Maxime Sempels More articles by this author C Austin Service More articles by this author Jay Simhan More articles by this author Faysal Yafi More articles by this author Martin Gross More articles by this author Expand All Advertisement PDF downloadLoading ...

Three-dimensional vortex dynamics and transitional flow induced by a circular cylinder placed near a plane wall with small gap ratios

The flow past a cylinder in proximity to a plane wall is investigated numerically for small gap ratios. Three vortex dynamic processes associated with different hairpin vortex generation mechanisms are identified for the first time, and the wake-induced turbulent transition is analysed. The vortex shedding is suppressed at $G/D = 0.1$ , while the spanwise vortex is generated via a Kelvin–Helmholtz instability and evolves into hairpin vortices. For $G/D= 0.3$ , the upper and lower rollers alternatively shedding from the cylinder, interact with the secondary vortex. The split secondary vortex merges with the upper roller and results in a new vortex downstream, which develops into hairpin vortices. When $G/D = 0.9$ , the secondary vortex interacts with the lower roller and then evolves into hairpin vortices. A tertiary vortex induced by the secondary vortex is observed, rotating in the opposite direction to the secondary vortex the wake-induced transitions share the same route. The velocity fluctuations deviate from the optimal growth theory in the pre-transitional region. In the transitional region low-frequency disturbances penetrate the sheltering edge to generate streaks where the disturbance energy declines. In the turbulent region the logarithmic layer is formed, indicating that the turbulent equilibrium is established.

Three-dimensional direct numerical simulations of vortex-induced vibrations of a circular cylinder in proximity to a stationary wall

In this paper three-dimensional direct numerical simulations (3-D DNS) on vortex-induced vibrations of an elastically mounted circular cylinder near a stationary wall at a subcritical Reynolds number of 500 and a gap ratio of 0.8 are conducted. It is found that the three-dimensionality increases linearly with amplitude, leading to substantial variations in the vortex dynamics. The interactions of the vortices with the wall-generated boundary layer play significant roles in altering the cylinder vibration.

Three-dimensional flow past a circular cylinder in proximity to a stationary wall

In this paper, we present direct numerical simulations (DNS) of the three-dimensional flow around a circular cylinder near a stationary wall at the Reynolds number of 500. The gap (G) between the cylinder surface and the stationary wall varies in the range of 0–3.0D where D is the cylinder diameter. We observe that the proximity wall significantly affects the flow topology around the cylinder, which is characterized by the asymmetric wake, upward gap flow, and strong interactions of the cylinder vortices with the wall-generated boundary layer. Three flow regimes are identified with variations of the fluid forces and vortex dynamics. (i) Steady regime: at G/D < 0.3, vortex shedding is suppressed in the near wake, and scattered streamwise vortices form in the far wake where the upper side shear layer meets the stationary wall. No fluctuating forces act on the cylinder. (ii) Biased unsteady regime: at 0.3 ≤ G/D < 1.5, the gap flow deflects upward and the vortices shed from the gap side are significantly suppressed. The cylinder has enlarged fluctuating drag and lift forces with identical dominant frequencies. (iii) Parallel unsteady regime: at G/D ≥ 1.5, vortices shed from both sides of the cylinder are of almost identical intensities while the gap flow is approximately parallel to the wall. The vortex dynamics approaches that of an isolated circular cylinder in unconfined flows. Flow features of each regime are illuminated through the flow fields, vorticity contours, statistics of the enstrophies and gap flow, and pressure distribution on the cylinder surface. Finally, we investigate the critical gap ratio for the onset of the vortex-shedding of the upper shear layer and discuss the underlying physics. Moreover, we observe that the occurrence of the second harmonic lift and fundamental drag frequencies are resulted from the asymmetric wake because of the proximity of the stationary wall.

Sparse sensor-based cylinder flow estimation using artificial neural networks

Despite the rising use of machine learning for flow estimation problems, a standard set of flows from which estimators and predictors can be developed, compared and assessed is currently lacking within the fluid dynamics community. This work presents two challenge flow cases for the advancement of sparse sensor-based flow estimation techniques. Feedforward and long short-term memory neural networks are used in conjunction with the proper orthogonal decomposition to predict velocity fields in the wake of two cylinders in proximity using sparsely-placed pressure sensors.

Main results of the first Data Assimilation Challenge

This work presents the main results of the first Data Assimilation (DA) challenge, conducted within the framework of the European Union’s Horizon 2020 project HOMER (Holistic Optical Metrology for Aero-Elastic Research), grant agreement number 769237. The challenge was jointly organised by the research groups of DLR, ONERA and TU Delft. The same synthetic test case as in the Lagrangian Particle Tracking (LPT) challenge (also presented in this symposium) was considered, reproducing the flow in the wake of a cylinder in proximity of a flat wall. The participants were provided with three datasets containing the measured particles locations and their trajectories identification numbers, at increasing tracers concentrations from 0.04 to 1.4 particles/mm3 . The requested outputs were the three components of the velocity, the nine components of the velocity gradient and the static pressure, defined on a Cartesian grid at one specific time instant. The results were analysed in terms of errors of the output quantities and their distributions. Additionally, the performances of the different DA algorithms were compared with that of a standard linear interpolation approach. Although the velocity errors were found to be in the same range as those of the linear interpolation algorithm, typically between 3% and 12% of the bulk velocity, the use of the DA algorithms enabled an increase of the measurement spatial resolution by a factor between 3 and 4. The errors of the velocity gradient were of the order of 10-15% of the peak vorticity magnitude. Accurate pressure reconstruction was achieved in the flow field, whereas the evaluation of the surface pressure revealed more challenging.

Implications of the Overlapping Degree Between Proximal Fibula and Tibia for Placing the Optimal Syndesmotic Screw: A Virtual Cadaveric Study.

To determine the optimal direction of the syndesmotic screw and to introduce a consistent landmark for practical application by analyzing three-dimensional (3D) modeling and virtual implantation. A total of 105 cadaveric lower legs (50 males and 55 females; average height, 160.6 ± 7.1cm) were used to reconstruct a 3D model by using the Mimics® software and the joint morphology was evaluated. Syndesmotic cylinders (Ø3.5mm/Length 100mm) were transversely placed in the proximal end of the incisura fibularis for simulating screw fixation. The tibial proximal cylinder, which was tangent to the posterior tibial condyles, was traced and the angle between the two cylinders was measured as the tibial torsion angle (TTA). After rotating the syndesmotic cylinder parallel to the ground, the overlapping degree between the proximal fibula and tibia was assessed as a radiologic indicator. Concerning tibial torsion, the TTA was an average of 36.7° (range, 17.2°-54.4°; SD, 8.78) When the syndesmotic cylinder was rotated to be parallel to the ground, the proximal fibula had nonlinear or linear overlap with the lateral border of the tibia, regardless of the joint morphology. In this non-overlapping view, three Weber's indices for normal fibular length could be better visualized than the mortise view. The syndesmotic cylinder in the proximal end of the incisura fibularis could be consistently placed parallel to the ground by internally rotating the tibia until there was a nonlinear or linear overlap between the proximal fibula and the tibia, regardless of the joint morphology.

Influence of boundary layer thickness and gap ratios on three-dimensional flow characteristics around a circular cylinder in proximity to a bottom plane

Three-dimensional flow characteristics around a horizontal circular cylinder near a plane boundary are investigated using a Direct Numerical Simulation (DNS) at the Reynolds number of 350. The cylinder has a gap-to-diameter ratio G/D = 0.2, 0.6 and 1.0, with a boundary layer thickness-to-diameter ratio δ/D = 0, 0.7 and 1.6. The hydrodynamic forces, pressure distributions, vortex shedding patterns, wake transitions and flow three-dimensionality features are presented and discussed. The hydrodynamic forces and pressure distributions are strongly dependent on G/D and δ/D. The mean drag coefficient decreases with increasing δ/D, whereas the mean lift coefficient increases with decreasing G/D. The pressure coefficient distribution around the cylinder changes from being asymmetric to symmetric as G/D is increased from 0.2 to 1.0, resulting in a development from the suppressed state to the fully developed state of the vortex shedding. As for the vortex dynamics, the strength and size of primary vortices decrease with increasing δ/D. The crossing trajectories exhibiting an inversion on the position of clockwise and counterclockwise vortices can only be observed in the wake when G/D is greater than a critical value below which the vortex shedding is completely suppressed, and when the cylinder is partially immersed into the boundary layer (G/D < δ/D < G/D + 1). An intrinsic switching between the single- and dual-frequency modes of the drag coefficient is found to be related to a complex interaction between the boundary layer and the near-wake vortex shedding. For a specific G/D, the flow three-dimensionality represented by the spanwise kinetic energy is found to decrease with increasing δ/D. For a specific δ/D, the spanwise kinetic energy shows a non-monotonic trend with the variation of G/D.

Patient-Specific 3-Dimensional Printing Titanium Implant Biomechanical Evaluation for Complex Distal Femoral Open Fracture Reconstruction with Segmental Large Bone Defect: A Nonlinear Finite Element Analysis

This study proposes a novel titanium 3D printing patient-specific implant: a lightweight structure with enough biomechanical strength for a distal femur fracture with segmental large defect using nonlinear finite element (FE) analysis. CT scanning images were processed to identify the size and shape of a large bone defect in the right distal femur of a young patient. A novel titanium implant was designed with a proximal cylinder tube for increasing mechanical stability, proximal/distal shells for increasing bone ingrowth contact areas, and lattice mesh at the outer surface to provide space for morselized cancellous bone grafting. The implant was fixed by transverse screws at the proximal/distal host bone. A pre-contoured locking plate was applied at the lateral site to secure the whole construct. A FE model with nonlinear contact element implant-bone interfaces was constructed to perform simulations for three clinical stages under single leg standing load conditions. The three stages were the initial postoperative period, fracture healing, and post fracture healing and locking plate removal. The results showed that the maximum implant von Mises stress reached 1318 MPa at the sharp angles of the outer mesh structure, exceeding the titanium destruction value (1000 MPa) and requiring round mesh angles to decrease the stress in the initial postoperative period. Bone stress values were found decreasing all the way from the postoperative period to fracture healing and locking plate removal. The overall construct deformation value reached 4.8 mm in the postoperative period, 2.5 mm with fracture healing assisted by the locking plate, and 2.1 mm after locking plate removal. The strain value at the proximal/distal implant-bone interfaces were valuable in inducing bone grafting in the initial postoperative period. The proposed patient-specific 3D printed implant is biomechanically stable for treating distal femoral fractures with large defect. It provides excellent lightweight structure, proximal/distal bone ingrowth contact areas, and implant rounded outer lattice mesh for morselized cancellous bone grafting.

Vortex-induced vibrations of two inline circular cylinders in proximity to a stationary wall

Vortex-induced vibrations of two inline circular cylinders in proximity to a stationary wall are numerically studied using the immersed boundary method at a Reynolds number of 100. Two cylinders, having the same degree of freedom (DOF), can oscillate only in the transverse direction (1-DOF) or in both the transverse and streamwise directions (2-DOF). The center-to-center spacings (L) of the two cylinders are 1.5D, 3.0D and 5.0D, respectively, while the gaps (G) between the wall and the cylinders are 0.6D, 1.5D and ∞, respectively. Here, D is the diameter of the cylinders. The mass ratio is 2.0 and the reduced velocity varies from 2.0 to 15.0, with the minimum interval of 0.1. We observe that the responses of the two cylinders are significantly influenced by the presence of a stationary wall, compared with those without near-wall effects. First, several hysteretic regions are observed at different gap ratios and spacing ratios. Second, the streamwise vibration amplitude is comparable to the transverse one in the 2-DOF cases. Third, the trajectories can be oval-shaped, figure-of-eight-shaped, quasi-periodic or chaotic depending on G and L. In the simulated parametric space, we divide the vibration response of the two cylinders into different branches, i.e., two stationary branches (SB-I and SB-II), two vibration branches (VB-I and VB-II), and one collision branch (CB). The features such as vibration amplitudes, vibration frequencies, wake patterns, fluid forces, mean position shifts, and vibration trajectories in each branch are explored in detail. Furthermore, the mechanisms of the excitation of the large-amplitude vibrations in both the streamwise and transverse directions are investigated.

306 Penile Wobble Effect: Proximal Corporal Dilatation as a Cause of Penile Prosthesis Failure

Penile structural defects may contribute toward penile prosthesis (PP) surgical complications or suboptimal outcomes such as distortion, angulation, extrusion, and crossover. We describe an observation of proximal corporal dilatation that affects PP device function. A retrospective analysis of Johns Hopkins institutional database of all patients who had PP surgery, from January 2013 to March 2017, was done. All cases of penile structural defects requiring surgical correction were identified. Data retrieved included demographics, causes of erectile dysfunction, number and causes of previous revisions, and surgical outcomes. We identified nine patients with proximal corporal dilatations (proximally from the penoscrotal junction), who required surgical revisions. Seven patients reported intact cycling PP devices, although they were unsteady and not usable; 2 reported devices that were not operational. Mean age at revision was 64.2+/-7.7 years (IQR 60-67). Mean elapsed time having PP devices was 15.1+/-14.1 years (IQR 4.5-24.5). Mean number of previous revisions was 2.4+/-3.3 times, and maximum revision number was 11 times. Causes of revisions commonly included replacement of intact but unstable PP devices (77.8%). The etiologies of erectile dysfunction were veno-occlusive disease in four patients (44.4%), post-radical prostatectomy in three patients (33.3%), pelvic trauma in one patient (11.1%), and vasculogenic in one patient (11.1%). Intraoperatively, eight patients (88.9%) had unilateral and one patient (11.1%) had bilateral corporal dilatations. Seven patients had intact cycling PP (77.8%), one had coexistent proximal cylinder rupture (11.1%), and one had mechanical failure (11.1%). All underwent reduction corporoplasty with PP removal and replacement. No perioperative adverse events occurred. All patients reported PP stability and satisfaction after revision with 7.5 months’ median follow-up time.

Freely vibrating circular cylinder in the vicinity of fully developed scour holes at low Reynolds numbers

In this work, a numerical study is conducted on the flow past an elastically mounted circular cylinder with two degrees of freedom (2-DoF) placed in the vicinity of a fully developed scour hole in both two-dimension (2D) and three-dimension (3D). This paper focuses to study how different fully developed scour profiles affect the hydrodynamic quantities of vortex-induced vibrations (VIV) of an elastically mounted circular cylinder in proximity and the flow fields. To begin with, we systematically conduct the 2D simulations at Reynolds number of Re=200 in the laminar flow regime and characterize the cylinder amplitudes, the hydrodynamic force coefficients and phase differences. For the 2D study, two representative fully developed scour hole profiles with Shields parameters of θ*=0.098 and 0.048 are considered and the case of a plane wall (i.e. θ*=∞) is taken into account as a reference for comparison. In the 3D simulations at Re=300, which is at the beginning of the subcritical flow regime, with θ*=0.098, the cylinder response characteristics and the 3D flow fields are investigated. It is shown that the upper boundary of the lock-in regime at θ*=0.048 is much smaller than those of θ*=0.098 and ∞, and the vortex shedding is ceased for Ur ≥ 5.3 at θ*=0.048. It is also found that the equilibrium scour profile affects the mean force coefficients to a large extent: the mean lift coefficient CL¯ for θ*=∞ is larger than those of θ*=0.098 and 0.048 in the pre-lock-in and post-lock-in regimes; and the mean drag coefficient CD¯ for θ*=∞ is larger than those of θ*=0.098 and 0.048 in all regimes.

Numerical simulations of steady flow over a circular cylinder near a boundary

A well-developed numerical scheme is used to simulate the steady current over a circular cylinder in proximity with a rigid plane at low Reynolds numbers. The numerical results, including the hydrodynamic forces acting on the cylinder and the flow fields, are obtained and discussed. The reduction of the vorticity generated at the cylinder surface of the gap side is attributed to the decrease of the amplitude of harmonic force components and eventually causes the complete suppression of the vortex shedding process. Particularly, a distinct flow scenario characterized by the agglomeration of two adjacent vortices takes place in the wake when the cylinder is positioned close to the free-slip wall just before the complete cessation of the vortex shedding. This finding might be served to explain the disappearance of regularly arranged vortices observed when the cylinder was towed above the stationary wall in the experiment. In contrast, the flow with a no-slip plane is also considered. The effective gap between the cylinder and the plane is reduced due to the presence of the boundary layer near the plane, and earlier cessation of vortex shedding is observed in comparison with that in the situations of free-slip plane.