Flutter Control Research Articles

Evaluation of secondary refinement procedures following free microvascular tissue reconstruction of the upper extremity

The primary cosmetic and functional outcome following successful upper limb salvage using free tissue transfer can often be unfavourable, which may motivate patients to undergo secondary procedures. In this study, we sought to identify predictors for secondary procedures and to analyse the type and number of these procedures. Patients who underwent free tissue transfer to the upper extremity between 2010 and 2017 were included in a retrospective cohort study: patients with secondary procedures to optimise the functional and aesthetic flap design (S cohort) vs. control cohort (C cohort). A multivariate regression analysis was used to identify predictors for secondary procedures. One hundred and twenty-eight patients were included in the study (S cohort 36, C cohort 92). All in all, 56 secondary refinement procedures were performed in a mean of eight months after the initial free flap reconstruction. Most of the defects in the S cohort were localised at the hand (53 %), and upper limb salvage was mostly accomplished by fasciocutaneous and adipocutaneous free flaps (S cohort 89 %). The most frequently performed secondary refinement procedures were direct partial flap excision (61 %), followed by liposuction (16 %) and the combination of both (17 %). Furthermore, 64 % of the secondary refinement procedures from the S cohort were combined with further surgical interventions to improve hand function, e. g. tenolysis and arthrolysis. Patients with defects of the hand received secondary procedures 2.4 times more frequently (p = 0.05). Also, patients with a good general health condition (ASA 1 and 2) were six times more likely to undergo a secondary procedure (p = 0.03). Secondary procedures are safe and frequently requested by patients following successful free flap upper limb salvage. In particular, this applies to patients who are in a good health condition and with free flaps to the hand. Therefore, we recommend the implementation of secondary refinement procedures in the reconstructive plan to increase patient compliance and satisfaction.

Numerical Evaluation of Structural Safety of Linear Actuator for Flap Control of Aircraft Based on Airworthiness Standard

Airworthiness standards of Korea recommend verifying structural safety by experimental tests and analytical methods, owing to the development of analysis technology. In this study, we propose a methodology to verify the structural safety of aircraft components based on airworthiness requirements using an analytical method. The structural safety and fatigue integrity of a linear actuator for flap control of aircraft was evaluated through numerical analysis. The static and fatigue analyses for the given loads obtained from the multibody dynamics analysis were performed using the finite element method. Subsequently, the margin of safety and vulnerable area were acquired and the feasibility of the structural safety evaluation using the analytical method was confirmed. The proposed numerical analysis method in this study can be adopted as an analytical verification methodology for the airworthiness standards of civilian aircraft in Korea.

Peritoneal flap for lymphocele prophylaxis following robotic-assisted laparoscopic radical prostatectomy with pelvic lymph node dissection: study protocol and trial update for the randomized controlled PELYCAN study

BackgroundData from interventional studies suggest that a peritoneal flap after pelvic lymph node dissection (LND) during laparoscopic, robotic-assisted radical prostatectomy (RARP) may reduce the rate of symptomatic lymphoceles in transperitoneal approach. However, most of these studies are not conducted in a randomized controlled fashion, thus limiting their scientific value. A recent prospective, randomized, controlled trial (RCT) did not show superiority of a peritoneal flap while further trials are lacking. Therefore, the aim of the presented RCT will be to show that creating a peritoneal flap decreases the rate of symptomatic lymphoceles compared to the current standard procedure without creation of a flap.Methods/designPELYCAN is a parallel-group, patient- and assessor-blinded, phase III, adaptive randomized controlled superiority trial. Men with histologically confirmed prostate cancer who undergo transperitoneal RARP with pelvic LND will be randomly assigned in a 1:1 ratio to two groups—either with creating a peritoneal flap (PELYCAN) or without creating a peritoneal flap (control). Sample size calculation yielded a sample size of 300 with a planned interim analysis after 120 patients, which will be performed by an independent statistician. This provides a possibility for early stopping or sample size recalculation.Patients will be stratified for contributing factors for the development of postoperative lymphoceles. The primary outcome measure will be the rate of symptomatic lymphoceles in both groups within 6 months postoperatively. Patients and assessors will be blinded for the intervention until the end of the follow-up period of 6 months. The surgeon will be informed about the randomization result after performance of vesicourethral anastomosis. Secondary outcome measures include asymptomatic lymphoceles at the time of discharge and within 6 months of follow-up, postoperative complications, mortality, re-admission rate, and quality of life assessed by the EORTC QLQ-C30 questionnaire.DiscussionThe PELYCAN study is designed to assess whether the application of a peritoneal flap during RARP reduces the rate of symptomatic lymphoceles, as compared with the standard operation technique. In case of superiority of the intervention, this peritoneal flap may be suggested as a new standard of care.Trial registrationGerman Clinical Trials Register DRKS00016794. Registered on 14 May 2019.

Data-driven active flutter control of airfoil with input constraints based on adaptive dynamic programming method

The stable flight region can be extended by adding control flap at the wing trailing edge and combined with active control technology. We studied the active flutter control by considering the input constraints. By designing the data-driven optimal controller, the limit cycle oscillations of a typical two-dimensional airfoil wing can be suppressed with single trailing edge control surface. The traditional control methods always need a precise mathematical model of the system, which put high requirements on system modeling. In this study, a novel data-driven optimal controller is proposed by using the input–output data and without depending on the nonlinear system dynamic model. This model-free approach avoids the effects of modeling errors and system uncertainty. When the data-driven controller is applied, the limit cycle oscillation phenomenon of the airfoil wing is eliminated within several seconds. It can be seen from the numerical simulation result that the data-driven adaptive dynamic programming control method possess superiority and feasibility.

A New Study on the Gap Effect of an Airfoil with Active Flap Control Based on the Overset Grid Method

Rotors with active flap control have considerable potential in reducing vibration and noise and improving aerodynamic performance. However, due to the movement of the flap, there are unavoidable gaps between the components that will lead to significant changes in the aerodynamic characteristics. Moreover, considering the difficulties in motion modeling and the accuracy of the simulation of the flow field in such a narrow gap, carrying out related research is challenging; thus, there has been inadequate targeted research, and that which does exist requires supplementation. To carry out this challenging flow field simulation, the overset assembly algorithm proposed by the author in previous research is adopted in the present study. It is used to successfully assemble the narrow gap, and the accuracy of the simulation is fully verified by comparing the results with the actual experimental results and a grid study. Furthermore, to compensate for the lack of research and experiments on the gap effect, cases considering a complete range of gap widths from an absence of a gap to a width of 10% of the chord length are set up and carried out under the following three case groups: steady cases with a fixed trailing-edge deflection angle, unsteady cases in which only the trailing-edge flap is flapping, and full-motion cases characterized by the periodic flap of the main airfoil and the trailing-edge flap. The results show that the gap increases the drag of the trailing-edge flap and decreases aerodynamic efficiency, especially at low speeds and high angles of attack. Nevertheless, when the gap is unavoidable, there is a range of the gap width that makes unapparent the decrease of aerodynamic efficiency. Moreover, the decrease of aerodynamic efficiency can be reduced as much as possible by a well-designed gap region geometry to ensure that the airfoil and the trailing-edge flap fit together when moving.

Flutter Control of Long Span Suspension Bridges in Time Domain Using Optimized TMD

Suspension bridges due to their long span are susceptible against dynamic events, like air flow which can cause considerable problems for them. Flutter, as an aerodynamic phenomenon, makes bridges vibrate, whereas their amplitude gradually diverges, needed the vibration control strategies. Tuned mass damper or in brief TMD, as the simplest passive device, can be used for this purpose. The performance of it can be enhanced when it’s parameters are adjusted to their optimum values. In this paper, the TMD was optimized by meta-heuristic optimization algorithms to control the flutter of long span suspension bridges. In this regard, the Golden Gate suspension bridge and Car tracking algorithm were selected for case study and optimization process, respectively. Firstly, the flutter analysis of bridge was done by multi-mode method in the time domain, and at second part, the TMD’s parameters were simultaneously optimized for maximum increase of flutter velocity of all the vulnerable modes. The results indicated that TMD was perfectly suitable device to control the flutter of long span bridges.

Fluid-structure coupled analysis of tandem 2D elastic panels

The aeroelastic characteristics of tandem positioned two-dimensional elastic panels have been numerically investigated. High-fidelity Computational Fluid Dynamics and Computational Structural Dynamics (CFD/CSD) methods have been used to simulate the aeroelastic interactions between the panels. Moreover, a CFD-based reduced order model is established through system identification method for auxiliary analyses. The results indicate strong fluid-mediated interactions between the adjacent panels. At low supersonic speeds, affected by the self-sustained vibration of upstream panel, the downstream panel exhibits the characteristics of forced vibration state for some parameter ranges where the flutter should occur. Beyond these parameter ranges, the vibration frequency of downstream panel gradually departs from the wake flow frequency and coincides with the flutter frequency of its isolated state, exhibiting the characteristics of limit cycle flutter. At high subsonic speeds, the aeroelastic response of downstream panel has a stabilizing effect on the upstream panel, and increases the dynamic stability of the entire tandem panels system. The aeroelastic behavior of the adjacent panels may enlighten a new perspective on the flutter control of the shell structures.

Effectiveness of Pre PRP Injection and Post Elevation Flap at Extended Random Flap Rat Skin

Background:Closure of the defect with a random skin flap is constrained by the extent of the defect area. Several studies have shown the benefits of administration of PRP (Platelet Rich Plasma) in random skin flap. The purpose of this study is to compare the effect of PRP injection given before flap elevation, after flap elevation and control on the extended random skin flap procedures in rats.Methods: This research is experimental with randomized post test only control group design (n = 27, divided into 3 treatment groups) that compare the effectiveness of PRP injection 24 hours prior to the elevation of the flap, after the elevation of the flap, and control in the extended random skin flap in rats. Random skin flap is made in the ratio 1: 5 on the rat skin. Measurement of viable area were observed on days 1, 7 and 14.Results: There were significantly increased viability of random skin flap on the group with PRP injection 24 hours prior flap elevation compared to other group of treatment. The average of viability on day first 39%±13% ;42%±34%; 62%±14%. On day 7th24%±13%; 36%±26%; 62%±12%.On day 14th16%±15%; 28%±22%; 60%±11%.Conclusion: Injection of PRP on extended random skin flap on rat 24 hours before flap elevationincrease viability of the flap compared to control group and group which receive PRP injection on extended random flap on rat skin after elevation of the flap. Viability increased due to angiogenesis stimulation after PRP injection.

Active control of sheet flutter by using injection and suction air flows from a nozzle

Active control of sheet flutter by using injection and suction air flows from a nozzle

Is There a Difference of Outcome of Patients who had no Previous DC-Cardioversion Versus Those who had Previous DC-Cardioversion: An Auckland Hospital Experience

DC-cardioversion (DCCV) is an intervention performed for achieving rhythm control for atrial fibrillation (AF) and atrial flutter (AFL). We performed a single-centre retrospective study to explore for any difference in outcome of patients who had their first DCCV versus those who had previous DCCV. Patients who underwent elective DCCV referred between referral dates 15 October 2010 to 30 January 2020 were included in this study. Primary endpoint was success rate of sinus rhythm maintenance at time of follow up. Secondary Results include difference in anti-arrhythmic agents utilised and electrophysiology (EP) procedures between the 2 groups. 410 patients had no previous DCCV, and 93 patients had ≥1 DCCV. Success rate of DCCV was similar at 90%. At follow up clinic, successful sinus rhythm maintenance in the no previous DCCV and ≥1 DCCV groups were 59% and 55%, respectively, p=0.09. More patients in the ≥1 DCCV were on amiodarone (39% vs 21%, p<0.001) and flecainide (14 vs 6%, p<0.01). A 15% increase in sotalol was recorded in both groups post-DCCV. 9% in the no previous DCCV and 26% in the ≥1 DCCV (p<0.0001) had AF ablation. More patients in the ≥1 DCCV group were on amiodarone and flecainide, whilst both groups recorded more patients being on sotalol post-DCCV. Successful DCCV was high at 90%. There was no difference in proportion of sinus rhythm during follow up clinic despite difference in anti-arrhythmic agents. This shows that some patients may be refractory to maintaining sinus rhythm and would be better off with a rate-control strategy.

Characteristics and Outcome of Patients who Underwent DC-Cardioversion: An Auckland Hospital Experience

DC-cardioversion (DCCV) is an intervention performed for achieving rhythm control for atrial fibrillation (AF) and atrial flutter (AFL). We performed a single-centre retrospective study to explore the clinical characteristics and outcome of patients who underwent DCCV.

Merits of conjunctival frill incision in reducing trabeculectomy-induced astigmatism and patient discomfort.

Purpose:To compare results of a novel “conjunctival frill/smile incision” on surgically induced astigmatism (SIA) and patient discomfort vs conventional trabeculectomy in the initial postoperative period.Methods:Sixty trabeculectomy cases were subjected to either conjunctival frill incision, performed 1.5–2.0 mm from the limbus (study group) or conventional fornix-based conjunctival flap (control group). Corneal astigmatism and suture-induced discomfort were assessed by keratometry and a self-devised patient questionnaire, respectively.Results:Both groups generated a “with the rule” SIA, which was 1.77 vs 2.42 at 1 week and reduced to 1.27 vs 1.8 in the study vs control group, after removal of sutures – both scleral flap releasable and conjunctival at 1 month. Patient discomfort score revealed enhanced comfort in 37% of patients (study group) vs 17% (control group) during the early postoperative period. After 1 month of surgery, good comfort was regained in all cases.Conclusion:This novel suturing technique results in reduced SIA, patient discomfort during the 1st month after trabeculectomy.

Simulation of Square Cluster Planting

Introduction. For cultivated crops, the optimal form of spacing is square form, which is provided by the square cluster method of planting. Currently, due to the high metal consumption and low productivity, this method of planting has been replaced with a single-seed planting one. But this does not solve the problem of rational distribution of seeds in the field, so the problem of plant spacing with the use of the optimal square form of spacing is relevant. The aim of the study is to develop and analyze a simulation model of square cluster planting based on an algorithm for controlling the executive mechanisms of the seeder sections using devices for local coordination of the seeding apparatus. Materials and Methods. A programmable square cluster planting using local coordination of the seeding apparatus and an algorithm for its realization are considered. The article describes the construction of a simulation model of sowing planting in Simulink Matlab with justification of its elements. The seed spreading in furrows and the seeder variable speed are taken into account. The number of pulses per revolution of the encoder shaft is theoretically justified. Results. The graphs of the distance traveled, positions coordinates of the flap opening and control signals depending on the time are constructed. The analysis of the encoder settings is carried out. When varied the plant spacing and the coordinates of the first flap opening, the dimension of the last seed cluster changes in the range from –2.6 ∙ 10–3 to 2.7 ∙ 10–3 m. With the increase in the seeder speed from 1.5 to 3.0 m/s, the mathematical expectation of the seed cluster dimensions increase from 0.054 to 0.218 m, and the coefficient of variation decreases from 61.2 to 15.0%. Discussion and Conclusion. The analysis of the simulation model of the square cluster planting showed that the algorithm for controlling executive mechanisms together with the local coordination system works adequately and provides high precision of placing seed clusters in the field. The dependences of the optimal number of pulses per an encoder shaft revolution on the specified seed spacing and radius of the track measuring wheel are determined. It was determined that the maximum dimension of the last seed cluster does not exceed 2.7 mm per 1 000 m (for x = 0.3 m and t = 0.7 m). It was found that the precision of the distribution of seed clusters in the field is determined more by the seeder speed than by the settings of the measuring device.

Prediction and active suppression of flutter in composite panel based on eigenvector orientation method

In this paper, the critical points of flutter of a composite panel predicted using a finite element model are studied using an eigenvector orientation method. Taking a supersonic simply supported panel and clamped panel models as examples, the accuracy of the eigenvector orientation method for predicting the critical points of flutter is verified, and the misjudgments of “channeling” (modal crossover) and other phenomena by traditional judgment methods are avoided. The piezoelectric actuators are combined with the upper and lower surfaces of the simply supported panel (clamped panel), and the aerodynamic parameters of each finite element are changed by activating the piezoelectric actuators. Based on linear quadratic adjustment theory, an optimal control method for the active flutter suppression is designed. The influence of the activation position of the different piezoelectric actuators on the critical points of flutter is studied to increase the flutter speed to an ideal range. The results show that the control torque generated by the piezoelectric actuators can offset the occurrence of flutter and provide a lead time for possible flutter control.

Damping Material for Stabilization of Panel Flutter at High Supersonic Speed

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Panel Flutter Control at High Supersonic Speed Using Piezoelectric Material (Dept.M)

Exterior panels forming the skin of flight vehicles traveling through the atmosphere at high supersonic speed are often susceptible to the occurrence of limit-cycle type self excited vibrations called flutter. The development of methods for panel flutter control is desirable and it is the objective of this work by using piezoelectric materials. The nonlinear equations of motion for panel flutter using Von-Karman's large deflection plate theory and the quasi-steady aerodynamic theory are modified to consider the composite plate with the piezoelectric layer. The composite plate consists of two piezoelectric layers bonded perfectly to the upper and lower surface of the original panel layer. When a voltage is applied to the piezoelectric layers, an induced strain in the plate material takes place and consequently tensile in-plane load is obtained. These tensile loads shift the onset of flutter point to about twice the value of the critical dynamic pressure for the plate alone. The values of control voltage and the effect of piezoelectric material properties are investigated. The method gives good results and succeeds in suppressing the panel flutter at its operating condition.

항공기 플랩 제어용 선형 구동장치 상세 설계 모델과 성능 시험리그의 구조 안전성 평가

본 연구에서는 항공기의 플랩 제어용 선형 구동장치의 상세 설계 모델과 구동장치 성능 시험리그의 기계적 거동과 안전성을 검토하였다. 구동장치와 시험리그를 대상으로 운용 조건에 대한 다물체 동역학 분석을 수행하였고, 기구학적 거동을 분석하여 시험리그의 유압 실린더 위치를 재선정하였다. 또한, 동역학 분석을 통해 부품의 반력과 경계 조건을 도출하여 유한요소 해석 기반의 구조 해석에 반영하였고, 물성 시험을 통해 확보한 소재의 항복 강도를 바탕으로 안전율을 산출하였다. 그 결과, 제안된 선형 구동장치의 상세 설계 모델과 성능 시험리그는 구조적으로 안전함을 확인하였다.

Active flutter control of the wind turbines using double-pitched blades

Classical flutter of a wind turbine blade is a concerned issue to hinder the wind utilization to a large extent. Recent predictions showed a decreasing flutter margin (the ratio of flutter speed to rated rotor speed) with the increase in wind turbine size. To address this issue, a new blade configuration called the double-pitched blade is proposed and analytically investigated for its potential to enhance the flutter suppressing capability of modern large-size wind turbine blades. This new blade comprise an inner part and a tip part, where the tip part can rotate (or pitch) independently with respect to the inner part through a tip actuator commanded by a feedback control law. The aerodynamic loads of blade tip due to the actively controlled rotation of the tip part provide a torque on the inner part, which provides damping for the torsional mode of the wind turbine blade. The effectiveness of this new double-pitched blade for suppressing flutter is verified through a simulation study conducted on a 907-DOF aero-servo-elastic wind turbine model. Parametric studies are performed on two main design parameters, i.e. the length of the tip part and the associated chordwise location of tip shaft with respected to the blade cross section, and flutter control performance are obtained by numerical optimization process. Simulation results show the optimal length of tip part is around 3.3%of blade length, and the associated chordwise location of tip shaft is around 45%of chord length, the flutter amplitude of the conventional blade can be mitigated to around 4%using this double-pitched blade.

Simulation of oscillating trailing edge flaps on wind turbine blades using ranging fidelity tools

AbstractRecent research developments have indicated that substantial reduction of both the fatigue and ultimate loads can be achieved by adopting trailing edge (TE) flap control strategies. Their aeroelastic tools employ blade element momentum (BEM) aerodynamic models enhanced with a sectional 2D treatment of the TE flap, neglecting the 3D effect of the trailed vorticity in the vicinity of the moving flap. In the present paper, a cross comparison of the BEM‐based models used in the aeroelastic analysis tools against higher fidelity, free‐wake lifting line, and fully resolved CFD models is performed, with the aim to highlight limitations of the first. A second level of comparison assesses the differences among tools of the same level of fidelity from different research groups. Moreover, a number of engineering‐based correction models that are used in conjunction with BEM and account for the complex 3D trailed vorticity effect are assessed. Simulations of a stiff rotor configuration of the DTU 10 MW Reference Wind Turbine are performed for a prescribed, harmonic TE flap motion, and aerodynamic loads are compared at the sectional and rotor‐integrated level. For the studied stiff rotor with the chosen flaps configuration, the results of the code‐to‐code comparisons indicate that low‐fidelity BEM tools consistently predict 1P variations of the rotor thrust due to the TE flap motion, but fail to reproduce the details of the load distributions especially in the vicinity of the flap section. BEM‐based corrected models, which account for 3D‐induced velocity effects, provide load distribution predictions closer to higher fidelity free‐wake and CFD models.

Effectiveness of Pre PRP Injection and Post Elevation Flap at Extended Random Flap Rat Skin

Closure of the defect with a random skin flap is constrained by the extent of the defect area. Several studies have shown the benefits of administration of PRP (Platelet Rich Plasma) in random skin flap. The purpose of this study is to compare the effect of PRP injection given before flap elevation, after flap elevation and control on the extended random skin flap procedures in rats. This was an experimental study with randomized posttest-only control group design (n=27, divided into 3 treatment groups) that compare the effectiveness of PRP injection 24 hours prior to the elevation of the flap, after the elevation of the flap, and control in the extended random skin flap in rats. Random skin flap is made in the ratio 1: 5 on the rat skin. Measurement of viable area were observed on days 1, 7 and 14. There were significantly increased viability of random skin flap on the group with PRP injection 24 hours prior flap elevation compared to other group of treatment. The average of viability on day first 39%±13% ;42%±34%; 62%±14%. On day 7th 24%±13%; 36%±26%; 62%±12%. On day 14th 16%±15%; 28%±22%; 60%±11%. Injection of PRP on extended random skin flap on rat 24 hours before flap elevation increase viability of the flap compared to control group and group which receive PRP injection on extended random flap on rat skin after elevation of the flap. Viability increased due to angiogenesis stimulation after PRP injection.