Wall Blowing Research Articles

Accidental High Voltage Electrocution Leading To Abdominal Wall Blow Out With Omental Evisceration And Auto Amputation Of Right Upper Limb: An Unusual Presentation

Electricity is the backbone for modern industrialization, development and day to day needs. Electrical Injuries are among the most devastating of burn injuries. High voltage electrical injuries result in extensive deep tissue damage and are associated with multiple complications and a high mortality rate. The passage of electric current through the body, produces wide range of effects, varying from insignificant localised spasm, little or no contact burns, or extreme severe burns. We describe the case of a 6-year-old child who suffered high voltage electric injury leading to anterior abdominal wall blow out with omental evisceration and auto amputation of right forearm. He was initially resuscitated in emergency room followed by emergency exploratory laparotomy was done with primary repair of ileal perforation along with right arm 4 quadrant amputation. This paper also emphasizes the safety measures to be taken at work place pertaining to high voltage cable

Adjoint-based linear sensitivity of a supersonic boundary layer to steady wall blowing–suction/heating–cooling

For a Mach $4.5$ flat-plate adiabatic boundary layer, we study the sensitivity of the first, second Mack modes and streaks to steady wall-normal blowing/suction and wall heat flux. The global instabilities are characterised in frequency space with resolvent gains and their gradients with respect to wall-boundary conditions are derived through a Lagrangian-based method. The implementation is performed in the open-source high-order finite-volume code BROADCAST and algorithmic differentiation is used to access the high-order state derivatives of the discretised governing equations. For the second Mack mode, the resolvent optimal gain decreases when suction is applied upstream of Fedorov's mode $S$ /mode $F$ synchronisation point, leading to stabilisation, and the converse when applied downstream. The largest suction gradient is in the region of branch I of mode $S$ neutral curve. For heat-flux control, strong heating at the leading edge stabilises both the first and second Mack modes, the former being more sensitive to wall-temperature control. Streaks are less sensitive to any boundary control in comparison with the Mack modes. Eventually, we show that an optimal actuator consisting of a single steady heating strip located close to the leading edge manages to damp the linear growth of all three instability mechanisms.

Reinforcement learning of control strategies for reducing skin friction drag in a fully developed turbulent channel flow

Reinforcement learning is applied to the development of control strategies in order to reduce skin friction drag in a fully developed turbulent channel flow at a low Reynolds number. Motivated by the so-called opposition control (Choi et al., J. Fluid Mech., vol. 253, 1993, pp. 509–543), in which a control input is applied so as to cancel the wall-normal velocity fluctuation on a detection plane at a certain distance from the wall, we consider wall blowing and suction as a control input, and its spatial distribution is determined by the instantaneous streamwise and wall-normal velocity fluctuations at distance 15 wall units above the wall. A deep neural network is used to express the nonlinear relationship between the sensing information and the control input, and it is trained so as to maximize the expected long-term reward, i.e. drag reduction. When only the wall-normal velocity fluctuation is measured and a linear network is used, the present framework reproduces successfully the optimal linear weight for the opposition control reported in a previous study (Chung & Talha, Phys. Fluids, vol. 23, 2011, 025102). In contrast, when a nonlinear network is used, more complex control strategies based on the instantaneous streamwise and wall-normal velocity fluctuations are obtained. Specifically, the obtained control strategies switch abruptly between strong wall blowing and suction for downwelling of a high-speed fluid towards the wall and upwelling of a low-speed fluid away from the wall, respectively. Extracting key features from the obtained policies allows us to develop novel control strategies leading to drag reduction rates as high as 37 %, which is higher than the 23 % achieved by the conventional opposition control at the same Reynolds number. Finding such an effective and nonlinear control policy is quite difficult by relying solely on human insights. The present results indicate that reinforcement learning can be a novel framework for the development of effective control strategies through systematic learning based on a large number of trials.

On the drag reduction mechanism of hypersonic turbulent boundary layers subject to heated wall blowing

Turbulence drag reduction is of great significance for the range increase of hypersonic flight vehicles. The proposed velocity-temperature coupling control method (Liu et al, Phys Rev Fluids 6:044603, 2021) is further extended to the hypersonic turbulent boundary layer. Direct numerical simulation results of four comparative cases show that the heated wall blowing achieves a drag reduction rate of 10.58%, which is about the sum of wall blowing (5.27%) and wall heating (6.35%). By evaluating the control efficiency, however, it is found that heated wall blowing is not as good as wall blowing and cannot obtain net energy saving rate. The modified FIK decompositions of skin friction coefficient indicate that the cliffy decrease of the mean convection term is the primary contribution for the drag reduction. Effects of the proposed control measure on turbulence statistics and coherent structures are also analyzed. Streamwise vortex is found to be away from the wall, thus leading to a lower friction drag.

Turbulence control for drag reduction through deep reinforcement learning

Deep reinforcement learning was applied to turbulence control for drag reduction in direct numerical simulation of turbulent channel flow. The learning determines the optimal distribution of wall blowing and suction based on the wall shear stress information. From an investigation of the optimal actuation fields, two distinct drag reduction mechanisms were identified. One of them, which had not previously been recognized, attempts to cancel the near-wall sweep and ejection events.

Artículo traducido] Configuración y localización óptima de los tornillos posteriores en las fracturas de calcáneo Sanders 2B: estudio biomecánico

BackgroundCalcaneal fractures can be high energy intra-articular injuries associated with joint depression. Challenges to fracture reduction include lateral wall blow out, medial wall overlap, comminution and central bone loss. Secondary deformity such as hindfoot varus alters foot biomechanics. Minimally invasive approaches with indirect reduction of the calcaneal tuberosity to maintain the reduction using posterior screws is routinely being used in the treatment of joint depression fractures. Biomechanically, optimum screw numbers and configuration is not known. Biomechanical studies have evaluated and proposed different screw configurations, however, it is not clear which configuration best controls varus deformity. This study aims to determine the optimum screw configuration to control varus deformity in Sanders 2B calcaneal fractures. MethodsSawbone models were prepared to replicate Sanders type 2-B fracture, with central bone loss and comminution. 0.5 cm medial wedge of the calcaneal tuberosity was removed to create varus instability. After stabilising posterior facet with a single 4 mm partial threaded screw, and applied an 8 hole contoured plate to stabilise the angle of Gissane, inserted one or two 7 mm cannulated partially threaded CharlotteTM (Wright Medical Technology, Memphis, USA) Headless Multi-use Compression (under image guidance) extra screws to control varus and subsidence deformity of the fracture. Coronal plane displacement of the dissociated calcaneal tuberosity fragment relative to the body when applying 5 N, 10 N and 20 N force was measured in millimetres (mm). Results2 screws inserted (one medial screw into the sustentaculum talus from inferior to superior and, one lateral screw into the long axis anterior process) provides the least displacement (0.88 ± 0.390 at 5 N and 1.7 ± 1.251 at 20 N) and the most stable construct (p < 0.05) when compared to other configurations. A single medial screw into the sustentaculum tali (conf. 3) resulted in the least stable construct and most displacement (4.04 ± 0.971 at 5 N and 11.24 ± 7.590 at 20 N) (p < 0.05). ConclusionThis study demonstrates the optimal screw configuration to resist varus in calcaneal fractures using minimally invasive techniques. Optimal stability is achieved using 2 screws; one located along the long axis of the calcaneus (varus control) and the other placed in the short axis directed towards the posterior facet of the calcaneus (control varus and subsidence). Further cadaver research would help evaluate optimal screw placement in simulated fractures to further assess reproducibility.

Effective aero-optical suppression by steady wall blowing and wall suction schemes for supersonic turbulent boundary layer

AbstractAs a basic flow model for engineering applications, wall-bounded turbulent flow has been widely studied in the field of aero-optics, but the flow control methods that could effectively suppress aero-optical effects are relatively rare. As an urgent requirement in engineering application, the concept of the steady wall blowing and suction is proposed by the author. Firstly, the author briefly described the flow model and physical method. Secondly, the choice of disturbance type is given. Then, the results of wall blowing-suction, suction and blowing ways based on steady and unsteady disturbance are compared. Finally, it is concluded that employing the high steady wall blowing disturbance (A = 0.2) could realise aero-optical suppression by around 20%. Besides, the steady wall suction scheme contributes to about 70%–80% reduction effect within a wide amplitude range (A = 0.2–1.0), which suppresses this effect by maintaining laminar state downstream contrasted by the baseline case.

Optimal posterior screw placement configuration in Sanders 2B calcaneal fractures: A biomechanical study

BackgroundCalcaneal fractures can be high energy intra-articular injuries associated with joint depression. Challenges to fracture reduction include lateral wall blow out, medial wall overlap, comminution and central bone loss. Secondary deformity such as hindfoot varus alters foot biomechanics. Minimally invasive approaches with indirect reduction of the calcaneal tuberosity to maintain the reduction using posterior screws is routinely being used in the treatment of joint depression fractures. Biomechanically, optimum screw numbers and configuration is not known. Biomechanical studies have evaluated and proposed different screw configurations, however, it is not clear which configuration best controls varus deformity. This study aims to determine the optimum screw configuration to control varus deformity in Sanders 2B calcaneal fractures. MethodsSawbone models were prepared to replicate Sanders type 2-B fracture, with central bone loss and comminution. 0.5cm medial wedge of the calcaneal tuberosity was removed to create varus instability. After stabilising posterior facet with a single 4mm partial threaded screw, and applied an 8 hole contoured plate to stabilise the angle of Gissane, inserted one or two 7mm cannulated partially threaded Charlotte™ (Wright Medical Technology, Inc. 5677 Airline Road Arlington, TN) Headless Multi-use Compression (under image guidance) extra screws to control varus and subsidence deformity of the fracture. Coronal plane displacement of the dissociated calcaneal tuberosity fragment relative to the body when applying 5N, 10N and 20N force was measured in millimetres (mm). Results2 screws inserted (one medial screw into the sustentaculum talus from inferior to superior and, one lateral screw into the long axis anterior process) provides the least displacement (0.88±0.390 at 5N and 1.7±1.251 at 20N) and the most stable construct (p<0.05) when compared to other configurations. A single medial screw into the sustentaculum tali (conf. 3) resulted in the least stable construct and most displacement (4.04±0.971 at 5N and 11.24±7.590 at 20N) (p<0.05). ConclusionThis study demonstrates the optimal screw configuration to resist varus in calcaneal fractures using minimally invasive techniques. Optimal stability is achieved using 2 screws; one located along the long axis of the calcaneus (varus control) and the other placed in the short axis directed towards the posterior facet of the calcaneus (control varus and subsidence). Further cadaver research would help evaluate optimal screw placement in simulated fractures to further assess reproducibility.

Skin-friction and heat-transfer decompositions in hypersonic transitional and turbulent boundary layers

The decompositions of the skin-friction and heat-transfer coefficients based on the twofold repeated integration in hypersonic transitional and turbulent boundary layers are analysed to give some major reasons of the overshoot phenomena of the wall skin friction and heat transfer. It is shown that the overshoot of the skin-friction coefficient is mainly caused by the drastic change of the mean velocity profiles, especially the strong negative streamwise gradient of the mean streamwise velocity far from the wall; and the overshoot of the heat-transfer coefficient is primarily due to the viscous dissipation, especially the strong positive vertical gradient of the mean streamwise velocity near the wall. These observations are different from the previous observations that the Reynolds shear stress and Reynolds heat flux are the reasons, respectively. Further investigations show that the above observations are independent of the set-up of the wall blowing and suction parameters, which indicates the universality of the major reasons of the overshoot phenomena in our numerical simulations. In the hypersonic turbulent boundary layers, it is observed that the strongly cooled wall temperature and the high Mach number can slightly enhance the contribution of the Reynolds shear stress, and weaken the contribution of the mean convection, mainly due to the strong compressibility effect. Moreover, the magnitudes of the relative contributions of the mean convection, pressure dilatation, viscous dissipation and the Reynolds heat flux increase as the wall temperature increases.

Pneumocephalus after surgical treatment of NOE fracture: Case report

Introduction: Naso-orbital-ethmoidal fractures are complex fractures involving the bones of the nose, orbit region, maxilla and ethmoid. This complex structure has a close relationship with the brain and the orbital region, which frequently suffer injuries during trauma. Among traumatic brain injuries, there is the pneumoencephalon. The present study aims to report the treatment of a patient who suffered an accident involving a rural animal. Case Report: A 63-year-old male patient was brought to the highly complex hospital for the Oral and Maxillofacial Surgery and Traumatology service, five days after the trauma. The physical examination showed traumatic telecanthus,anisocoria and mydriasis of the right eye, right eyelid ptosis, laceration in the right eyebrow and deviation of the nasal bone to the left. In the imaging exam (computed tomography), traces of fractures were observed in the nasal bone region, medial orbital wall, infra-orbital margin, frontal-zygomatic pillar and right orbital blow out fracture. After a surgical approach to fix the fractures, it was observed the development of a hypodense area in the intracranial region, suggestive of pneumocephalus. Conclusion: These complications, such as pneumocephalus, must be diagnosed early and appropriate treatment must be started as soon as possible to reduce possible sequelae, requiring the intervention of a multidisciplinary team.

Control of roughness-induced transition under the influence of inflow disturbance

Control of roughness-induced transition influenced by two- or three-dimensional inflow disturbances using spanwise-uniform wall blowing is investigated from the perspective of unstable modal growth with direct numerical simulations. Visualization of flow structures for two-dimensional disturbances indicates that the counter-rotating vortex pair in the wake bends the high-shear layer, which is related to both symmetric and antisymmetric unstable modes. The interaction of these structures is found to be responsible for the initial growth of the symmetric mode, which dominates the transition process. Both upstream and downstream position wall blowing are effective for transition control. Upstream position blowing works by lifting up the boundary layer and diminishing the wake structures, resulting in inhibition of the symmetric mode. Downstream position blowing has an even better effect, attributable to reconfiguration of the streamwise vorticity field in the wake and further distortion of the high-shear layer. When the inflow disturbance is a three-dimensional wave, the antisymmetric mode becomes dominant in the near-wake region, resulting in more rapid initial growth of the symmetric mode. As oblique waves have higher growth rates in a compressible boundary layer, the background disturbance is obviously stronger. Therefore, transition occurs earlier than for two-dimensional disturbances. When upstream position blowing is introduced, the spanwise shear related to the antisymmetric mode is reduced, and the background disturbance is suppressed as the disturbed boundary layer is pushed away from the roughness. Downstream position blowing can still inhibit the symmetric mode, but the antisymmetric mode is barely influenced, since this blowing is less effective in suppressing the counter-rotating vortex pair.

Drag reduction in turbulent channel flows by a spanwise traveling wave of wall blowing and suction

A spanwise traveling wave, generated by blowing and suction at walls, is applied in direct numerical simulations to reduce the drag in a fully developed turbulent channel flow with Reτ≈180. The wave traveling direction reverses periodically to induce a spanwise motion of the flow near the wall, similar to that from spanwise wall oscillations. Such a motion can be approximated by an infinite series of the Stokes layers in an asymptotic expansion. A relation linking the blowing and suction velocity and frequency for the traveling wave is derived to achieve a drag reduction similar to the case with spanwise wall oscillation. A drag reduction of 24% is achieved in the present study. From the analyses of the energy budget of Reynolds stresses, the drag reduction mechanism is found strongly related to the pressure–strain correlations. The reduced wall-normal strain rate and pressure–strain correlation are the main causes of the decrease in energy components of turbulence. The induced spanwise motion also weakens the streamwise strain rate through inclining the vortex structures periodically and modulates the spanwise strain rate through its production term.

Flow structure and heat transfer of transpiration cooling by using a LBM: The effects of wall blowing and spatially nonuniform injection

Considering the effects of wall bowing and spatially nonuniform injection, the near-wall flow structures and heat transfer characteristics in transpiration cooling are studied through numerical simulations by an in-house thermal lattice Boltzmann solver accelerated by GPGPUs. Results reveal that the development of coolant layer is influenced by local velocity gradients, and a wall blowing ratio of larger than 2%–3% induces the flow separation and unstable coverage of low-temperature layer, and that the coolant injection weakens the surface friction coefficient, while the flow separation facilitates a local increase of the skin friction coefficient downstream the wall. For nonuniform injection, the local increases of mass and momentum with the peak velocity of nonuniform injection is beneficial to the coolant-layer development but the spatial temperature control is unstable, indicating the stable development and coverage of coolant layer are the key factors of the flow and heat transfer in transpiration cooling process.

Direct numerical simulation of roughness-induced transition controlled by two-dimensional wall blowing

Abstract

CT Scan Assessment of Femoral Tunnel Location in ACL Reconstruction Performed During Initial Phase of the Learning Curve

Introduction:During anterior cruciate ligament (ACL) reconstruction, femoral tunnelling is one of the most imperative stage. The success of surgical reconstructions of the ACL depends on the accurate restoration of its anatomy. The significance of the location of the hole drilled in femur has been repeatedly highlighted in ACL reconstruction. Incorrect tunnel placement is not infrequent, and even with diligent training, and aids, surgeons may still have difficulty in correctly positioning tunnels intra-operatively. Usually susceptible are surgeons in initial phase of the learning curve.Objective:To determine the susceptibility of surgeons in initial phase of learning curve while drilling femoral tunnel.Methods:All patients diagnosed with ACL rupture at a single institution between August 2018 and September 2019 were considered for the study. The surgeons who were relatively new out of their fellowship and training programmes (average of less than one years of independent practice) performed all surgical reconstructions, the number of reconstructions done independently was also taken into consideration (average of less than five independent procedures done before commencement of this study). We used anatomic free hand technique using bony and anatomic indicators as our markers, assisted by ruler, to drill femoral tunnel. Every subject had an 128 slice 3D CT-Scan done in immediate post-op period. High resolution 3-Dimensional view was created of the knee to evaluate the tunnel location. The position of the femoral tunnel was evaluated using the Bernard and Hertel quadrant method. The Femoral tunnel location was expressed in terms of its distance from the notch and posterior wall of condyle, the results were expressed in terms of percentage.Results:A net total of 32 patients were included who underwent single bundle ACL reconstruction. In our study, measurement of femoral tunnel placement was - depth 37.1% and height 24.6%, represented as percentage depth (deep to shallow (t)) and height (high to low (h)). Our results were compared with other established studies. The value of height was near to that mentioned in literature; whereas the value of depth was shallower (or distal) when compared to established literature with average location being 10.7% shallower (or distal) to anteromedial bundle insertion mentioned in study by Colombet et al and 4.8% shallower when compared to study by Zantop et al. When compared to study by Bernard and Hertel the location is 12.3% shallower. The reason for comparison with anteromedial bundle is that in single bundle anatomical reconstruction Pearle et al , Segawa et al and Simmons et al advocate it to be anteromedial.Conclusion:The surgeons in initial phase of their learning curve may be more prone to shallow (non anatomic) location of femoral tunnel during single bundle ACL reconstruction. We infer that this discrepancy in proximal (deep) to distal (shallow) orientation is due to fear of posterior wall blow out, that is the violation of the posterior femoral cortex, a known intraoperative complication in ACL reconstruction.

Direct numerical simulations of a supersonic turbulent boundary layer subject to velocity-temperature coupled control

A velocity-temperature coupled control method is proposed for turbulence drag reduction of supersonic boundary layers. Direct numerical simulations indicate that heated wall blowing achieves the best drag reduction, whereas cooled wall blowing leads to a drag increase. The reduction of mean viscous shear stress is mainly responsible for the drag reduction mechanism, though there is a substantial increase in Reynolds stresses. Nevertheless, the control efficiency of heated wall blowing is low due to high energy consumption, but further investigation is needed.

Direct numerical simulations of supersonic turbulent boundary layer with streamwise-striped wall blowing

Direct numerical simulations of a spatially developing Ma 2.25 supersonic turbulent boundary layer with streamwise-striped wall blowing (SSB) are performed for the purpose of turbulence drag reduction. The SSB is designed to blow through long and straight slots in the flow direction. The slots are equally distributed in spanwise direction, with different stripe spacing and width. Blowing amplitudes of 0.1% and 0.2% are investigated. For comparison, uniform blowing (UB) of 0.1% is also simulated. It is found that in spite of weak control amplitudes, 7.4% and 14.5% drag reduction can be achieved in the case of 6SSB 0.1% and 6SSB 0.2%, respectively. Similar to UB, the boundary layer displacement thickness is thickened by SSB, with a thicker viscous sub-layer and a logarithmic zone which moving away from the wall. Turbulence intensities and turbulent coherent structures are enhanced, although the streamwise scales of the latter are attenuated. Turbulent kinetic energy analysis presents that both the production and dissipation are increased in the near wall. Compressible Renard-Deck decomposition of Cf shows that it is the spatially growth term that mainly responsible for the turbulence drag reduction.

Accidental high voltage electrocution causing abdominal wall blow out bowel evisceration: An unusual presentation

AI Publications is an open access peer review international journal to publish the article in the field of Agriculture, Horticulture, Food science, Rural Development, Environment and Health Research, Chemistry, Mathematics,Physics.

Comparative study of efficiency of PFN vs PFNA-II (Asian) in Intertrochanteric femur fracture with deficient lateral wall- A prospective interventional study

Background: Proximal femoral nail is the gold standard for many peri trochanteric fracture. Being a load bearing device and intramedullary implant theoretically it is superior than DHS. Lateral wall integrity is the major concern for varus collapse of fixation. Some recent studies reported many PFNA induced lateral wall blow out during insertion. PFNA II came with modifications to prevent these complications during insertion. PFN also has many complications like z effect, screw cut-out, migration and reverse z effect, varus collapse in deficient lateral wall. Hence, we conducted this study to analyse the efficiency of PFN vs PFNA II in lateral wall deficient unstable intertrochanteric fracture.Methods: It is a prospective interventional study involving 50 patients with intertrochanteric fracture having deficient lateral wall. Study conducted at our institution during 2017-2019. Patients were randomized into two groups of 25 each using computer-based randomization to be treated with PFN or PFNA-II. Post operatively followed at regular intervals and analyzed radiographically and functionally using x ray and Harris hip score respectively.Results: The average time to union radiologically was 25.2 weeks and 20.18 weeks for PFN and PFNA-II group respectively. The mean HHS accounted for 85.64 in PFN group and 88.45 in PFNA-II group at the end of study. In this study 12 patients had excellent HHS, 8 patients with good HHS, 3 fair HHS and 2 patients with poor HHS in PFN group whereas 14 patients have excellent HHS, 9 patients with good HHS, 1 fair and 1 patient with poor HHS in PFNA-II group. In PFN two patients suffered surgical site infection, two patients progressed to have varus collapse and screw backout. In PFNA II one patient had helical blade cut through. These failed implants patients underwent revision surgery.Conclusions: single helical blade with ability to create visible compression and impaction at fracture site has a clear advantage over PFN having two screws to be passed through deficient lateral wall. End cap with locking helical blade within the nail prevents its backout and reduces complications related to it. PFNA II is better than PFN in lateral wall deficient intertrochanteric femur fracture.

BHEL Smart Wall Blowing System: New Product Development in Manufacturing Industry

BHEL Smart Wall Blowing System: New Product Development in Manufacturing Industry