Length Of Cylinder Research Articles

SOLUTION OF THE LAPLACE EQUATION BY THE METHOD OF SEPARATION OF VARIABLES FOR A LENGTH HOLLOW CYLINDER

The physical model of many electrical objects is a hollow cylinder of finite length. As a basis for constructing analytical models of electrical machines, linear equations of mathematical physics are used. They are the solution of the Laplace three-dimensional partial differential equation, which is widely used in analytical calculations.
 
 The purpose of the study is to solve the Laplace three-dimensional differential equation for a hollow cylinder of finite length, which can be adapted for the electromagnetic calculation of electromechanical devices with cylindrical active parts.
 
 Materials and methods. To solve the Laplace equation in a cylindrical coordinate system, the Fourier variable separation method was used. To obtain a non-trivial solution of the equation, eigenfunctions of the Sturm–Liouville problem were used. Dirichlet, Neumann boundary value problems of the mixed type for hollow cylinders are adapted to the electromagnetic calculation of electromechanical devices having cylindrical active parts.
 
 The results of the study. The Laplace equation given in a cylindrical coordinate system is considered, on the basis of which the Sturm–Liouville equation with zero initial values is compiled to find eigenfunctions. The complete solution of the Lapalace equation with given boundary conditions is obtained as the sum of the solutions of two separate Dirichlet problems with different boundary conditions.
 
 Findings. The obtained analytical expression can be used as a mathematical basis for constructing three-dimensional analytical models of electrical machines with cylindrical active parts and carrying out electromagnetic calculations of the corresponding electromechanical devices.

Circumferential SH wave in piezo-reinforced composite structure with imperfect interface bonding

The present study fundamentally focuses on analyzing the limitations and transference of circumferential shear horizontal (CSH) waves in a four-layered compounded cylinder. The geometrical structure consists of cylinders of infinite length composed of self-reinforced (SR), fibre-reinforced (FR), piezo-magnetic (PM), and piezo-electric(PE) materials. In order to make the structure sensitive to the application pertaining to sensors and actuators, the PM and PE cylinders have been categorically placed in the outer part of the geometry. Whereas in order to provide stiffness and stability to the structure, the inner part consists of SR and FR materials. The common boundary between each of the cylinders has been essentially considered as imperfectly bounded. At the interface of PE and PM media, mechanical, electrical, magnetic, and inter-coupled types of imperfections have been exhibited. The closed-form of dispersion relation has been deduced for two contrast cases i.e. electrically open magnetically short (EOMS) and electrically short and magnetically open (ESMO) circuit conditions. Dispersion curves have been plotted to illustrate the salient features of parameters like normalized imperfect interface parameters, initial stresses, and radii of the concentric cylinders. The comparative effect of each one of these parameters on the phase velocity of the wave has been enlisted and marked individually. Every graph has been presented with two successive modes for a comprehensive understanding. This theoretical study may be implemented to improvise the performance of surface acoustic wave (SAW) sensors, actuators, and Piezo-cables in the form of Piezo-polymer sensors consisting of piezo-electric quartz, piezo-composite concentric cylinders, and coaxial piezo-cables.

Wake control of a square cylinder: Impinging the vortex cores with dual flexible splitter plates

Numerous works have been conducted to study the wake control of a bluff body and more efficient strategies are still what we seek for. This paper studies the complex fluid–structure interaction (FSI) problem of a square cylinder mounted with dual flexible splitter plates from a new perspective: impinging the vortex core with flapping plate tip. The Reynolds number (Re) based on the side length of the square cylinder is fixed at 332.6. The splitter plates are attached at both sides of the square cylinder. Structural parameters, such as plate length and bending stiffness, are considered to achieve an optimal arrangement of this configuration. Compared to the traditional single splitter plate arrangement, only a short splitter length is needed for this dual splitter plates configuration. Flow visualization indicates that the drag reduction is associated with the increase of base pressure and the lift suppression is related to the inhabitation of the interaction of the shear layer and split effect of the tip vortices. The dimensionless bending stiffness plays a vital role in determining the behavior of the splitter plate. Two vibration modes, i.e., off-center vibration and asymmetry vibration modes are captured and the up and down splitter plates tend to vibration in-phase. The Lissajous trajectories of the free tip mainly exhibits arc-shape and sickle-shape. Given the performance of the square cylinder-dual splitter plates configuration, splitter length of l/L=1.5 is an optimal configuration, which is less affected by flexural rigidity. The maximum drag reduction could reach 23.1% and the lift force exerting on this configuration does not increase significantly, which is beneficial for the structural stability.

THE APPLICATION OF BROWN SUGAR GRATER MACHINE TECHNOLOGY FOR GINGER FLAVOURED VARIANT

Brown sugar is one of the natural sweeteners in the community. Where the sale of brown sugar has fluctuated due to the constant demand for brown sugar. Researchers aim to increase productivity and increase interest in brown sugar, so a new product is made, namely brown sugar with a ginger flavor. Therefore, the researchers made a ginger- flavoured brown sugar machine as a souvenir drink typical of the city of Kediri with a capacity of 150 liters/hour. the method used is a design method, which includes the planning stage, calculation, manufacture or assembly, and testing the machine. Which in this section explain more on the transmission system, which cover electric. In the results of the report above, it can be concluded that the planning for the number of scar teeth obtained a cylinder length of 90 mm and a cylinder diameter of 50 mm and the distance between the teeth of the scar 1 and the teeth of the scar 2 is 3 mm and the number of teeth planned for scarring is 840 teeth of the scar. The correction factor has a value of 0.186 kW. In machine testing, the comparison results obtained that 20 liters of brown sugar requires 1.134 kg of ginger and the grating process takes 13 minutes. Using an electric motor as a power source with a size of 1/4 HP, 220 volts, 200 watts and a speed of 2800 rpm. The quality of the grated ginger produced is very soft motor dynamo, grater eye, grater cover, fiter

(516) Maximizing Penile Prosthesis Length: Our Technique and Outcomes

Abstract Introduction The most common cause of patient regret after penile prosthesis surgery is penile shortening, which has been reported in up to 70% of patients postoperatively. Objective We sought to query a national database on average prosthesis length and describe our techniques to maximize cylinder sizes. Methods We performed a retrospective review of the Coloplast database of 3-piece penile prosthesis cases performed over the span of 1 year nationally and by a single high volume surgeon and compared average cylinder lengths. Results Between July 1, 2021 and June 27, 2022, 145 three piece penile prosthesis surgeries were performed at our institution. All were performed via a scrotal incision. Nationally, 32.8% were performed infrapubic while 58.1% were performed scrotal. The most prevalent cylinder length in our series was 22cm, compared to the most prevalent nationally of 20cm. (Table 1). Our technique to maximize cylinder length involves circumferential mobilization of the corporal bodies and corporal tissue sparing. After initial scrotal incision and dissection to the level of the penile compartment, circumferential mobilization of the corporal bodies is carried out. In addition, the ventral corporal dartos layer is meticulously peeled away. Corporal tissue sparing is carried out by employing 9” Metzenbaum scissors rather than sequential dilators for corporal tunneling. (Image 1). The benefit of this approach is the ability to create a dorsal compartment to the level of the triangular ligament of the glans, thereby extending the space to the level of the midglans. This maneuver minimizes placement of the prosthesis anteriorly at the level of the fossa navicularis and prevents floppy glans that would otherwise compromise maximum cylinder length. Conclusions Three piece penile prosthesis cylinder size can be maximized by circumferential mobilization of the corporal bodies, corporal sparing maneuvers, and the utilization of long Metzenbaum scissors for precise corporal tunneling, ensuring the distal cylinder tips are seated within the tip of the glans rather than at the coronal sulcus. This can help mitigate patient regret after prosthesis surgery. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Coloplast

(346) Long Term Experience with AMS-700 CXR™ Prosthesis in High-Risk Patients with Corporal Fibrosis

Abstract Introduction Although commonly utilized for high-risk patients with corporal fibrosis, outcome data for narrow inflatable penile prosthesis (IPP) cylinders are relatively sparse. Objective The objective of this study is to assess the outcomes of a cohort of patients who underwent IPP placement with the AMS-700 CXR™ (CXR) cylinders at our tertiary referral center. Methods We retrospectively reviewed our institutional IPP database for patients who underwent CXR cylinder implantation between 2007 and 2021. Indications, clinical factors, and surgical outcomes were documented for all patients. Kaplan-Meier survival analysis was performed to illustrate implant survival. Patient satisfaction was assessed with a phone survey in which patients provided feedback on penile length, girth, rigidity, and overall satisfaction with the CXR implant. Results Among 1149 IPP surgeries reviewed during the study interval, 49 (4%) underwent CXR implantation with a mean (SD) age of 64 years (±11). Indications for CXR implantation included history of infected IPP (30/49, 62%), ischemic priapism 8/49 (16%), and idiopathic fibrosis (11/49, 22%). Postoperative complications occurred in 6/49 (12%) patients including infection 3/49 (6%), cylinder herniation 2/49 (4%), and glans necrosis 1/49 (2%). Discordant intraoperative corporal measurements were common (13/49, 27%), as were discordant rear tip extender lengths (16/49, 33%). The explantation and revision rates were 3/49 (6%) and 4/49 (8%), respectively. Forty percent (19/48) of patients were available for phone survey response (Figure). A total of 47% (9/19) of patients were dissatisfied with their implant, primarily due to perceived loss of penile length (12/19, 63%) and girth (10/19, 53%). Five (5/9, 55%) of these patients had a history of IPP explantation. Fifty-three percent (10/19) of those surveyed are still satisfied with their implant with 58% (11/19) pleased with the rigidity the CXR implant provides. Conclusions Narrow based inflatable penile implants have acceptable long-term survival. Cylinder lengths are often discordant in corporal fibrosis patients. Despite use in a high-risk group, patient satisfaction remains acceptable, although many complain of perceived loss of penile length and girth. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Boston Scientific, Coloplast.

(484) Single Dilation in Primary Inflatable Penile Prosthesis Placement is Associated with Less Corporal Complications than Sequential Dilation

Abstract Introduction In primary implant patients without significant corporal fibrosis, penile implant surgical technique varies in implementation of either single dilation (SingD) or sequential dilation (SeqD). Vigorous debate exists regarding both methods, but there is no robust evidence supporting one technique over the other in the literature. Objective We compared the rates of intraoperative complications and postoperative outcomes from a large international database of inflatable penile prostheses (IPP) performed by expert implant surgeons to determine if there were any significant differences in rates between SingD and SeqD. Methods We analyzed IPP cases performed by international implanters from 2016-2021. All primary implant cases were included, while revision cases, salvage operations, and patients with evidence of corporal fibrosis were excluded. Intraoperative complications and postoperative noninfectious outcomes were assessed between the two groups. These included proximal/distal perforation and cylinder crossover. Results After exclusion based on aforementioned criteria, we identified 3045 patients who underwent IPP. After 1:1 propensity matching of both groups, we analyzed 572 patients who underwent SingD and 572 patients who underwent SeqD. Between the two groups, more men of non-Caucasian race underwent SingD vs SeqD (p<0.001). There was a significant difference in cylinder length in the SeqD group vs the SingD group (20cm ± 1.5 vs. 20 cm ±2 respectively, p=0.018). There were 8 (0.7%) intraoperative complications in total, 7 in the SeqD group and 1 in the SingD group (p=0.034). Of these intraoperative complications, 3 (37.5%) patients who underwent SeqD sustained a proximal perforation, 3 (37.5%) sustained distal crossover, and 1 (12.5%) sustained proximal crossover. 1 patient (12.5%) with intraoperative complication who underwent SingD sustained a proximal perforation. Postoperatively, 78 (82%) of complications were in the SeqD group and 17 (18%) in the SingD group (p<0.001). Of these postoperative complications, there were 15 patients with bleeding or hematoma, of which 14 were in the SeqD group vs 1 in the SingD group (p<0.001). Of the 35 patients who were noted to have device-related malfunction, 29 underwent SeqD and 6 underwent SingD (p<0.001). Postoperative complications were more related to technical error in the SeqD vs the SingD group (11 patients and 1 patient respectively, p<0.011). On multivariate analysis, prior radical prostatectomy was predictive of intraoperative complications (OR 4.59 with IQR 1.39-15.16, p=0.024), while larger cylinder size seemed to be protective (OR 0.66 with IQR 0.50-0.89, p=0.006). On multivariate analysis, SeqD was predictive of postoperative complications (5.16 with IQR 3.01-8.83, p<0.001), as was history of priapism (4.15 with IQR 1.30-13.29, p=0.017). Patients who undergo SeqD may be calibrated by the surgeon to have more complex corpora, which could explain higher complication rates. We identified 3045 patients who underwent IPP. Conclusions In our international multicenter assessment of primary IPPs without corporal fibrosis performed by expert surgeons, patients undergoing single dilation appear to have slight benefit in total cylinder length. Sequential dilation may confer greater risk of intraoperative and postoperative complications, including bleeding and hematoma. Single dilation is a safe technique for primary inflatable penile prosthesis. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Coloplast and Boston Scientific

(507) Predictors of Postoperative IPP Length: A Multicenter, Multinational Analysis

Abstract Introduction Inflatable penile prosthesis (IPP) placement is associated with high postoperative patient satisfaction. Patients often express concerns about postoperative penile length. There is scant evidence in the literature of clinical and surgical factors that predict IPP length. Objective To evaluate predictors of cylinder length for men undergoing primary IPP placement in a large multicenter cohort. Methods Patients undergoing primary IPP placement for treatment of erectile dysfunction at 16 high-volume implant centers were included. All patients had preoperative demographics, surgical characteristics, and device length retrospectively collected at their respective institutions and combined for analysis. Descriptive statistics were reported for the full group. Univariate analysis was utilized to isolate variables significantly associated with device length and all variables reaching p<0.1 were included in linear regression modeling. Results 3,953 men underwent primary IPP placement. The mean age was 61.8±10.4 years and BMI was 29.8±4.2 kg/m2. The mean total device length was 20.6±2.1cm. 1291 (32.7%) had diabetes mellitus, 641 (16.2%) were smokers, 705 (17.8%) had a prior radical prostatectomy, 195 (4.9%) had prior radiation, 549 (13.9%) had Peyronie’s disease, and 884 (22.4%) had a history of intracavernosal injections. In univariate analysis, BMI (B=0.05, 95%CI 0.04 to 0.07, p<0.001), a history of Peyronie’s disease (20.4 vs 20.6cm, p=0.02), and use of intracavernosal injection (20.7 v 20.9cm, p=0.02) were predictors of shorter total device length. Use of rear tip extenders (20.7 v 20.0cm, p<0.001), penoscrotal approach (21.0 v 20.3, p<0.001), and single corporal dilation (20.8 v 20.4cm, p<0.001) were associated with longer length. In multivariable analysis, a history of Peyronie’s disease (B=-0.29, 95%CI -0.47 to -0.11, p=0.002) and greater BMI (B=0.05, 95%CI 0.03 to 0.07, p<0.001) were predictors of shorter total device length. Independent predictors of longer device length were penoscrotal approach (B=-0.85, 95%CI -1.03 to -0.65, p<0.001), rear tip extender use (B=1.00, 95%CI 0.84 to 1.17, p<0.001), and single corporal dilation (B=-0.5, 95%CI -0.67 to -0.34, p<0.001). Conclusions In this series, Peyronie’s disease and greater BMI are independent predictors of shorter IPP device length, while use of rear tip extenders, single corporal dilation, and penoscrotal approach are independent predictors of longer device length. These results are important in counseling patients regarding expectations of postoperative length. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Intuitive Surgical, Fidelis, Urofill, Boston Scientific, Endo Pharma, Coloplast, Cynosure, Antares Pharma, Clarus Pharmaceuticals, Acerus Pharma

Terahertz EPR spectroscopy using a 36-tesla high-homogeneity series-connected hybrid magnet

Electron Paramagnetic Resonance (EPR) is a powerful technique to study materials and biological samples on an atomic scale. High-field EPR in particular enables extracting very small g-anisotropies in organic radicals and half-filled 3d and 4f metal ions such as MnII (3d5) or GdIII (4f7), and resolving EPR signals from unpaired spins with very close g-values, both of which provide high-resolution details of the local atomic environment. Before the recent commissioning of the high-homogeneity Series Connected Hybrid magnet (SCH, superconducting + resistive) at the National High Magnetic Field Laboratory (NHMFL), the highest-field, high-resolution EPR spectrometer available was limited to 25 T using a purely resistive “Keck” magnet at the NHMFL. Herein, we report the first EPR experiments performed using the SCH magnet capable of reaching the field of 36 T, corresponding to an EPR frequency of 1 THz for g = 2. The magnet’s intrinsic homogeneity (25 ppm, that is 0.9 mT at 36 T over 1 cm diameter, 1 cm length cylinder) was previously established by NMR. We characterized the magnet’s temporal stability (5 ppm, which is 0.2 mT at 36 T over one-minute, the typical acquisition time) using 2,2-diphenyl-1-picrylhydrazyl (DPPH). This high resolution enables resolving the weak g-anisotropy of 1,3-bis(diphenylene)-2-phenylallyl (BDPA), Δg = 2.5 × 10–4 obtained from measurements at 932 GHz and 33 T. Subsequently, we recorded EPR spectra at multiple frequencies for two GdIII complexes with potential applications as spin labels. We demonstrated a significant reduction in line broadening in Gd[DTPA], attributed to second order zero field splitting, and a resolution enhancement of g-tensor anisotropy for Gd[sTPATCN]-SL.

Vortex-induced vibrations of tandem diamond cylinders: A novel lock-in behavior

This paper presents a comprehensive numerical investigation of the undamped, simultaneous in-line, and transverse flow-induced vibrations of two identical diamond cylinders (of cross-stream length D) in a tandem arrangement at a low Reynolds number (= 100) in uniform flow, using a stabilized space–time finite-element formulation. The study focuses on the effects of cylinder proximity and shape, considering diamond cylinders with a mass ratio of 10 and a separation distance of 5D and varying the reduced velocity from 1 to 20. The results reveal distinct lock-in behavior for the upstream and downstream cylinders, with a low-frequency extended lock-in phenomenon observed for the downstream cylinder. The motion trajectories of both cylinders exhibit a distinctive “raindrop-shaped” pattern. Notably, the synchronization zone shows a non-zero mean lift for a narrow range of reduced velocity. The study also identifies three distinct modes of vortex arrangement in the gap region between the cylinders. Comparing the findings for tandem diamond cylinders with those for single diamond and tandem square cylinders provides further evidence of the significant impact of proximity and shape on the vibration characteristics of the cylinders.

Mechanical indications for inflatable penile prosthesis revision: analysis and implications for revision surgery.

Despite technical advancements, inflatable penile prostheses (IPPs) are inherently at risk of mechanical failure given their nature as hydraulic devices. To characterize IPP component failure location at the time of device revision and stratify by manufacturer: American Medical Systems (Boston Scientific [BSCI]) and Coloplast (CP). A retrospective review of penile prosthesis cases from July 2007 to May 2022 was conducted, identifying men who underwent revision surgery. Cases were excluded if documentation did not denote the cause of failure or the manufacturer. Mechanical indications for surgery were categorized by location (eg, tubing, cylinder, or reservoir leak; pump malfunction). Nonmechanical revisions were excluded (component herniation, erosion, or crossover). Categorical variables were assessed with Fisher exact or chi-square analysis; Student t-test and Mann-Whitney U test were used for continuous variables. Primary outcomes included specific location of IPP mechanical failure among BSCI and CP devices and time to mechanical failure. We identified 276 revision procedures, 68 of which met inclusion criteria (46 BSCI and 22 CP). Revised CP devices were longer than BSCI devices (median cylinder length, 20vs 18cm; P < .001). Log-rank analysis revealed a similar time to mechanical failure between brands (P = .096). CP devices failed most often due to tubing fracture (19/22, 83%). BSCI devices had no predominant site of failure. Between manufacturers, tubing failure was more common in CP devices (19/22 vs 15/46 for BSCI, P < .001), while cylinder failure was more common among BSCI devices (10/46 vs 0/22 for CP, P = .026). The distribution of mechanical failure is significantly different between BSCI and CP devices; this has implications regarding the approach to revision surgery. This is the first study to directly compare when and where mechanical failure occurs in IPPs and to compare the 2 main manufacturers head-to-head. This study would be strengthened by being repeated in a multi-institutional fashion to provide more robust and objective evaluation. CP devices commonly failed at the tubing and rarely elsewhere, while BSCI devices showed no predominant failure site; these findings may inform decision making regarding revision surgery.

Wake Control of Flow Past Twin Cylinders via Small Cylinders

The drag and lift force of a twin-cylinder structure are often greater than those of a single cylinder, causing serious structural safety problems. However, there are few studies on the passive control of twin cylinders. The study aimed to investigate the performance of passive drag reduction measures using small cylinders on twin cylinders at a Reynolds number of 100. The effects of small cylinder height (HD/D = 0~1.0, D is the side length of the twin cylinder) and cross-sectional shape on fluid force and flow structures were studied by direct numerical simulations. The control mechanism was analyzed using high-order dynamic mode decomposition (HODMD). The results showed that significant drag reduction occurred in the co-shedding state, particularly when the gap length of the twin cylinders L/D = 6.0. The small control cylinders with HD = 0.6, by contrast, showed the best performance in reducing the mean drag and fluctuating lift of the twin cylinders. It reduced the mean drag of the upstream cylinder (UC) by 2.58% and the downstream cylinder (DC) by more than 62.97%. The fluctuating lift coefficient for UC (DC) was also decreased by more than 70.41% (59.74%). The flow structures showed that when the flow hit UC under the action of small control cylinders, a virtual missile-like aerodynamic shape was formed at the leading edge of UC. In this way, the gap vortex consisted of two asymmetric steady vortices and the vortex length significantly increased. This was also confirmed by HODMD. The coherence modes in the gap were suppressed and thus the interaction between gap flow and wake flow was mitigated, which resulted in the fluid force reduction.

Study of the Ejection Process of Cold Ejection System with Flexible Cylinder by Corpuscular Method

Cold ejection is widely used in the realm of ejection, but conventional ejection systems can’t adapt to the modern war due to obvious infrared characteristics and high energy consumption, so new ejection system is desired. This work demonstrates a new way of flexible ejection, which is based on control method and corpuscular Method. Firstly, a finite element model of the flexible cylinder ejection system is established. Then, the corpuscular method is applied to study the influence of length and cross-section diameters of the cylinder on the dynamic of ejection process. It is found that the length of flexible cylinder will prolong the time of ejection from 0.72s to 1.01s with length increase from 7.2m to 10.4m. However, the diameter decreases the ejection time. Meanwhile, the velocity increases from 14.37m/s to 15.46m/s with cross-section diameter of cylinder increases from 0.60m to 0.75m. And the maximum overload is bigger 25.9 % than minimum.

Rigorous Electrodynamic Analysis of a Cylindrical Lens Consisting of Hollow Perfectly Conductive Cylinders

A fast and rigorous method is developed for the electrodynamic analysis of an infinite cylindrical lens made of an artificial material, which is an array of hollow conducting cylinders of finite length and finite wall thickness, identically oriented along the lens axis. It is shown that the method makes it possible to calculate the characteristics of lenses consisting of multiple elements using a personal computer. The focusing properties of the lens are studied. The method is an alternative to and a technique to verify the approach based on the analysis of a lens made of a homogenized material with a refractive index of an infinite 3D photonic crystal.

Large-eddy simulations of the flow past a bluff-body with active flow control based on trapped vortex cells at Re = 50000

We investigate a novel flow control concept, which allows to govern bluff-body wake dynamics and the laminar–turbulent transition by suppressing vortex shedding and obtaining the mostly detached flow. Large-eddy simulations past a bluff-body (BB) with and without an active flow control (AFC) system at a Reynolds number of 50000 and zero angle of attack are presented. The BB is designed of a semicircular cylinder of the finite span-wise length with two hemispheres attached to its lateral sides. The BB has a negative lift force because of detached and attached massive recirculation zones, which respectively, originate from separation of the laminar boundary layers from its upper side and the leading edge. AFC is based on the two trapped vortex cells implemented at the upper side of BB to control the behavior of boundary layers. The chosen AFC demonstrates almost the detached flow and suppresses the vortex street. The lift-to-drag ratio of BB with integrated AFC is calculated as ≈1.5 (compared to ≈−1 obtained for the simple BB) coupled with reasonable energy losses of 10% in terms of the total drag coefficient. Finally, present findings demonstrate the potential of the concept and provide the basis for its further development.

Analysis of Flow Characteristics around a Square Cylinder with Boundary Constraint

Based on the two-dimensional hydrodynamic model of the finite volume method and structured multigrid, the flow characteristics around a square cylinder with boundary constraint are analysed. The gap ratio G/D (G is the distance from the cylinder to the channel boundary, and D is the side length of the square cylinder) does not change the four flow patterns. Under the laminar vortex street phase, the boundary constraint only reduces the scale of the vortices. The vortex centres are pressed toward the boundaries of the channel, and a low velocity zone is formed near the boundary, but the law of vorticity attenuation along the flow direction is not changed. The flow pattern classification map shows that the boundary constraint increases the Reynolds number required to generate the turbulence flow pattern, and the range of the Reynolds number in the flow pattern of the laminar vortex street has a maximum increase range. The correlation between the time-averaged drag coefficient or the vortex shedding frequency and Reynolds number under different gap ratios indicates that the resistance of the square cylinder and the vortex shedding frequency increase accordingly with the strengthening of the boundary constraint. When G/D &lt; 3.5, the increase is particularly obvious. Meanwhile, the correlation characteristics between the resistance or the vortex shedding frequency of the square cylinder and the Reynolds number are unrelated to the boundary constraint strength.

Self-adaptive turbulence eddy simulation of flow control for drag reduction around a square cylinder with an upstream rod

The use of an upstream circular rod to control the flow around a downstream square cylinder is found to efficiently reduce the drag of the square cylinder. The complex flow characteristics and mechanism of the rod-square system in tandem arrangement as a passive flow control method for various centre-to- centre gap ratios (L/D) are investigated by numerical simulation. Turbulence modelling of the rod-square cylinder system is challenging. To select a suitable turbulence modelling, the recently developed Self-Adaptive Turbulence Eddy Simulations (SATES), as well as IDDES (Improved Delayed Detached Eddy Simulation) and SBES (Stress Blended Eddy Simulation) are first assessed for single circular and single square cylinder flow test cases. The SATES method performs best among the three models for bluff body flow simulation and is thus used in the drag flow control study. For the rod-square flow control system, the Reynolds number is 34000 based on freestream velocity U0 and the edge length of the square cylinder D. The diameter of the control rod is kept constant at d/D = 0.18. The flow characteristics and mechanism are explored in detail, varying the rod and square cylinder distance of L/D = 1.5, 2.0, 2.5and 3.0. According to the absence or presence of vortex shedding from the upstream rod cylinder, two flow patterns (pattern I and pattern II) are observed. Large drag reduction is observed for all the simulation cases the maximum drag reduction is approximately 63% with L/D = 2.0, and the minimum drag reduction approximately 53% with L/D = 3.0. The secondary lock-frequency, which presents as pattern II, is caused by the excitation of upstream vortices. It is found that the side recirculation is associated with the wake recirculation length of the square cylinder, which is similar to the elongated cylinder in the flow pattern I. The flow mechanism of suppression of the vortices from the rod can be attributed to the effective diffusion of vorticity in the separating shear layer caused by the presence of the front wall of the square cylinder.

Experimental Study of Turbulent Wake Flow Around Trapezoidal Cylinders With Varying Streamwise Aspect Ratios

AbstractThe effects of streamwise aspect ratio (AR) on the asymmetric wake flow over and behind right-angled trapezoidal cylinders with AR (= upper cylinder length to height ratio) = 1, 2, 3, 4, and 5 were investigated using particle image velocimetry. The Reynolds number based on the freestream velocity and cylinder height was 14700. The flow characteristics are examined in terms of the mean velocity flow, Reynolds stresses, probability density function (PDF), and two-point correlations. The results show that the primary vortex in the AR1 and AR2 trapezoidal cases extends into the wake region but is confined to the surface of the longer cases and two asymmetrical wake vortexes are only observed in the longer cases. Dual peaks of elevated streamwise Reynolds stresses are observed in the wake region, regardless of the aspect ratios. The magnitudes of the Reynolds stresses and turbulent kinetic energy are higher in the shorter cases (AR1, AR2, and AR3 cases) compared to the longer cases. The PDF distributions show a bimodal asymmetrical shape in the shorter cases but a nearly Gaussian distribution in the AR5 case. Two-point autocorrelations of the streamwise and vertical velocity fluctuations revealed that the spatial coherency of the turbulent structures is highly sensitive to the streamwise aspect ratio and reference locations. Systematic comparison between the present asymmetric results and symmetric wakes generated by rectangular cylinders with similar aspect ratios and Reynolds number shows significant differences between the asymmetric and symmetric wakes, especially at smaller aspect ratios.

Numerical study on wake control of square cylinder based on vertical axis wind turbines

A large eddy simulation is used in this study to explore wake control for a square cylinder based on vertical axis wind turbines. These vertical axis wind turbines are installed around a chamfered square cylinder, and the effects of the wind turbine diameter and the spacing between the wind turbine and the chamfered square cylinder on the aerodynamic forces and wake characteristics of the chamfered square cylinder are investigated. The analysis results indicate that wind turbines continuously transport high-speed fluid to the wake and the negative pressure value in the square cylinder wake decreases, which leads to a reduction in the downwind drag. Further, the time-averaged main vortex in the chamfered square cylinder wake is elongated and the center of the main vortex is farther away from the square cylinder; this considerably reduces the surface pressure and lift coefficient fluctuation. The optimal control effect for the square cylinder wake is obtained when h is 1/8d and the ratio of d to D (the side length of square cylinder) is 0.25. Compared with the results of flow around an uncontrolled chamfered square cylinder, the root mean square value of the lift coefficient and the mean value of the drag coefficient are reduced by 80.5% and 19.8%, respectively. Thus, the aerodynamic control method based on the vertical axis wind turbines can effectively suppress the vortex shedding mode of a square-cylinder wake, so as to reduce the aerodynamic forces and vortex-induced vibration.

Electrophoresis of a small sphere in a cylinder of finite length.

The pressure due to electrophoretic motion of a charged colloidal sphere in a fluid-filled circular cylinder is determined in the limit in which the sphere radius is small compared with that of the cylinder. If the ends of the cylinder are open, pressure-driven Poiseuille flow occurs, but the magnitude of this flow is shown to be small when the cylinder is long compared to its radius. It is concluded that the flow has little effect upon electrophoretic velocities, unlike when the diameter of the sphere is comparable to that of the cylinder in which case the Poiseuille flow increases electrophoretic velocities and creates long-range interactions betweenspheres.