scholarly journals A Numerical Study on the Thermocapillary Migration of Droplet under Microgravity with Periodic Thermal Boundaries by Front Tracking Method

2021 ◽  
Author(s):  
Ying Zhang ◽  
Ziqiang Ma ◽  
Mengjun Yao ◽  
Hui Gao ◽  
Xun Xu
Keyword(s):  
Numerical Study ◽  
Movement Time ◽  
Phase Interface ◽  
Front Tracking ◽  
Movement Direction ◽  
Cycle Period ◽  
Temperature Phase ◽  
Navier Stokes Equation ◽  
Thermocapillary Migration ◽  
Initial Movement

This paper mainly studied the thermocapillary migration of deformable droplets induced by periodic temperature boundary under microgravity conditions. The Finite-Difference/Front-Tracking (FD/FT) Method was used to solve the Navier-Stokes equation coupled with the energy equation, and the Continuum Surface Force (CSF) model was used to simplify the surface tension of the phase interface. The results showed that the maximum droplet migration velocity increased with the increase of temperature amplitude. And the droplet cycle period became shorter with the increase of temperature angular frequency. In the 1/4 cycle, the initial movement time of droplet decreased with the increase of temperature phase. If the phase was reversed, the initial movement direction of the droplet changed. With the increase of Reynolds number (Re), the droplet tended to maintain its motion inertia.

Numerical Study on Control of Sunroof Buffeting

2021 ◽  
Vol 13 (2) ◽  
Author(s):  
K. Vijaykumar ◽  
S. Poonkodi ◽  
A.T. Sriram
Keyword(s):  
Numerical Study ◽  
Leading Edge ◽  
Dominant Frequency ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Ansys Fluent ◽  
Flow Modification ◽  
Numerical Result ◽  
Modification Technique ◽  
Commercial Solver

Sunroof has become one of the essential features of a luxury car, and it provides natural air circulation and good illumination into the car. But the primary problem associated with it is the buffeting noise which causes discomfort to the passengers. Though adequate studies were carried out on sunroof buffeting, efficient control techniques are needed to be developed from fundamental mechanism. To reduce the buffeting noise, flow modifications at the entrance of the sunroof is considered in this study. The internal portion of the car with sunroof is simplified into a shear driven open cavity, and two-dimensional numerical simulations are carried out using commercial solver, ANSYS Fluent. Reynolds averaged Navier-Stokes equation is used with the realizable k-? turbulence model. The unsteady numerical result obtained in this study is validated with the available experimental results for the dominant frequency. The prediction is good agreement with experiment. Flow modification technique is proposed to control the sunroof buffeting by implementing geometric modifications. A hump has been placed near the leading edge of the cavity which resulted in significant reduction of pressure oscillations. Parametric studies have been performed by varying the height of hump and the distance of hump from the leading edge. There is no prominent difference when the height of the hump is varied. As the distance of the hump from the leading edge is reduced, the sound pressure level decreases.

Factors Affecting Remote Positioning Performance

1995 ◽  
Vol 39 (4) ◽  
pp. 282-286
Author(s):  
Shang H. Hsu ◽  
Chien C. Huang
Keyword(s):  
Movement Time ◽  
Interactive Effect ◽  
Vertical Movement ◽  
Movement Direction ◽  
Movement Amplitude ◽  
Distance Ratio ◽  
Factors Affecting ◽  
Fitts Law ◽  
Movement Distance ◽  
Two Measures

The purpose of this study was to investigate the effects of target width, movement direction, movement amplitude, and remote distance on remote positioning performance. Movement time and movement distance ratio were taken as measures of remote positioning performance. It was found that the effects of target width, movement amplitude, and movement direction on the two measures were significant. The effect of remote distance was significant only for movement distance ratio. The magnitude of the effect of target width on movement time was larger than that of movement amplitude; a modification of Fitts' Law was thus proposed. Moreover, there was an interactive effect between target width and movement direction- i.e., movement direction had an effect only when the target width was small. Among the eight movement directions, upward vertical movement was the best for remote positioning. The results shed some light onto the design of remote control user interface.

scholarly journals Mean field dynamo action in shear flows. I: fixed kinetic helicity

2020 ◽  
Vol 495 (4) ◽  
pp. 4557-4569 ◽  
Author(s):  
Naveen Jingade ◽  
Nishant K Singh
Keyword(s):  
Magnetic Field ◽  
Mean Field ◽  
Magnetic Activity ◽  
Turnover Time ◽  
Cycle Period ◽  
Dynamo Action ◽  
Navier Stokes Equation ◽  
Axisymmetric Mode ◽  
Dynamo Wave ◽  
Mean Field Dynamo

ABSTRACT We study mean field dynamo action in a background linear shear flow by employing pulsed renewing flows with fixed kinetic helicity and non-zero correlation time (τ). We use plane shearing waves in terms of time-dependent exact solutions to the Navier–Stokes equation as derived by Singh & Sridhar (2017). This allows us to self-consistently include the anisotropic effects of shear on the stochastic flow. We determine the average response tensor governing the evolution of mean magnetic field, and study the properties of its eigenvalues that yield the growth rate (γ) and the cycle period (Pcyc) of the mean magnetic field. Both, γ and the wavenumber corresponding to the fastest growing axisymmetric mode vary non-monotonically with shear rate S when τ is comparable to the eddy turnover time T, in which case, we also find quenching of dynamo when shear becomes too strong. When $\tau /T\sim {\cal O}(1)$, the cycle period (Pcyc) of growing dynamo wave scales with shear as Pcyc ∝ |S|−1 at small shear, and it becomes nearly independent of shear as shear becomes too strong. This asymptotic behaviour at weak and strong shear has implications for magnetic activity cycles of stars in recent observations. Our study thus essentially generalizes the standard αΩ (or α2Ω) dynamo as also the α effect is affected by shear and the modelled random flow has a finite memory.

scholarly journals Numerical study of dendritic growth during solidification using front-tracking method

2016 ◽  
Vol 745 ◽  
pp. 032128
Author(s):  
Mohamad Ali Jaafar ◽  
Stéphane Gibout ◽  
Daniel Rousse ◽  
Jean-Pierre Bédécarrats
Keyword(s):  
Dendritic Growth ◽  
Numerical Study ◽  
Front Tracking ◽  
Tracking Method ◽  
Front Tracking Method

A Numerical Study on the Influence of Grooves on Heat Transfer Performance of Wet Clutch

2012 ◽  
Vol 249-250 ◽  
pp. 517-522 ◽  
Author(s):  
Yu Long Lei ◽  
Jie Tao Wen ◽  
Xing Zhong Li ◽  
Cheng Yang
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Three Dimensional ◽  
Friction Material ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Linear Distribution ◽  
Exchange Performance ◽  
Wet Clutch ◽  
Oil Flow

In order to evaluate the efficacy of grooves on cooling performance of wet clutch, a numerical analysis based on the computational fluid dynamics (CFD) code FLUENT is presented in this study. This analysis is based on the numerical solution of the three-dimensional Navier-Stokes equation, coupled with the energy equation in the flow and the heat conduction equations in the friction material and the core disk. The turbulence characteristics were predicted using RNGk-ε model. The flow field and temperature distributions in radial grooves are obtained. It is shown that radial grooves possess the highest heat exchange performance at the entrance and is not linear distribution in the radial direction and cooling oil flow has a little effect on the highest temperature of friction plate. With the developed analysis method, it is possible to easily and quickly investigate the heat transfer behaviour of wet cluth with groove patterns.

scholarly journals Learning feedback and feedforward control in a mirror-reversed visual environment

2015 ◽  
Vol 114 (4) ◽  
pp. 2187-2193 ◽  
Author(s):  
Shoko Kasuga ◽  
Sebastian Telgen ◽  
Junichi Ushiba ◽  
Daichi Nozaki ◽  
Jörn Diedrichsen
Keyword(s):  
Feedback Control ◽  
Visual Information ◽  
Feedforward Control ◽  
Control Policy ◽  
Movement Direction ◽  
Common Mechanism ◽  
Central Target ◽  
Online Corrections ◽  
Online Feedback ◽  
Initial Movement

When we learn a novel task, the motor system needs to acquire both feedforward and feedback control. Currently, little is known about how the learning of these two mechanisms relate to each other. In the present study, we tested whether feedforward and feedback control need to be learned separately, or whether they are learned as common mechanism when a new control policy is acquired. Participants were trained to reach to two lateral and one central target in an environment with mirror (left-right)-reversed visual feedback. One group was allowed to make online movement corrections, whereas the other group only received visual information after the end of the movement. Learning of feedforward control was assessed by measuring the accuracy of the initial movement direction to lateral targets. Feedback control was measured in the responses to sudden visual perturbations of the cursor when reaching to the central target. Although feedforward control improved in both groups, it was significantly better when online corrections were not allowed. In contrast, feedback control only adaptively changed in participants who received online feedback and remained unchanged in the group without online corrections. Our findings suggest that when a new control policy is acquired, feedforward and feedback control are learned separately, and that there may be a trade-off in learning between feedback and feedforward controllers.

scholarly journals Numerical simulation of indoor microclimate using free software

2021 ◽  
Vol 33 (5) ◽  
pp. 259-270
Author(s):  
Anna Alexandrovna Tsynaeva ◽  
Ekaterina Alexandrovna Tsynaeva
Keyword(s):  
Numerical Simulation ◽  
Velocity Field ◽  
Numerical Solution ◽  
Thermal Energy ◽  
Numerical Study ◽  
Free Software ◽  
Momentum Balance ◽  
Navier Stokes Equation ◽  
Temperature Deviation ◽  
Residential Space

The work is devoted to the numerical study of indoor microclimate. Accurately predicting the distributed microclimate inside the residential space equipped with a microclimate control system called the «smart house» allows to save thermal energy significantly. Mathematical modeling was carried out by means of the Navier-Stokes equation, the energy equation, the continuity equation. The system of equations used was closed using the k-w-sst turbulence model. The resulting numerical solution was performed in the Code_Saturn, which has a free license. The Salome free software package was used to build a grid. In this context, a second–order scheme (SOLU) was used to resolve the velocity field, a MULTIGRID scheme was used for the pressure field, automatic settings were used for the kinetic energy of turbulence and her dissipation and for the temperature field, the maximum number of iterations for each cycle was equal to 10000, the Solver Precision accuracy was 10-8. The SIMPLEC algorithm is used to obtain a connected solution of the momentum balance and continuity equations. The paper provides an example of numerical solution verification, which is showed the relative temperature deviation from the values obtained by other authors was no more than 0.8-1.2%. Numerical simulation of the air velocity field in the residential space showed values from 0.12 to 0.15 m/s. Based on the results of the obtained solution, an analysis of the saving of thermal energy was carried out when regulating the supply of heat.

scholarly journals Numerical study of flow across an ellipse and a circle placed in a uniform stream of infinite extent

2020 ◽  
Author(s):  
Adnan Anwar ◽  
Mudassar Razzaq ◽  
Liudmila Rivkind
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Reynolds Number Flow ◽  
Infinite Extent ◽  
Number Flow ◽  
Conforming Finite Element Method ◽  
Drag And Lift

As an example of an aerodynamics prototypical study, we examined a two-dimensional low Reynolds number flow over obstacles immersed in a stream of infinite extent. The Navier Stokes equation is being discretized by non conforming finite element method approach. The resulting discretized nonlinear algebraic system is being solved by using the fixpoint method and the Newton method and multigrid method for the linear sub-problem employed. The magnitude of the uniform upstream velocity under the study of the problem for Reynolds number in the range 1 < Re < 100 and the angle of attack of the upstream velocity at α = -5; 0; 5 degrees performed. Analysis of the resulting drag and lift forces acting on obstacles with respect to the angle of attack of the upstream velocity and the Reynolds number is made. Moreover, the influence of one obstacle on the resulting drag and lift coefficients of other obstacles determined. The results are being presented in a graphical and vector form.

Optimization of a Peristaltic Micropump with Multiple Moving Actuators

2009 ◽  
Vol 6 (4) ◽  
pp. 189-197
Author(s):  
Ravi Bhadauria ◽  
Ramana M. Pidaparti ◽  
Mohamed Gad-el-Hak
Keyword(s):  
Interaction Analysis ◽  
Numerical Study ◽  
Exact Analytical Solution ◽  
Navier Stokes ◽  
Actuation Frequency ◽  
Navier Stokes Equation ◽  
Specific Flow ◽  
Flow Rates ◽  
Fluid Analysis ◽  
Peristaltic Micropump

A design optimization based on coupled solid–fluid analysis is investigated in this paper to achieve specific flow rate through a peristaltic micropump. A micropump consisting of four pneumatically actuated nozzle/diffuser shaped moving actuators on the sidewalls is considered for numerical study. These actuators are used to create pressure difference in the four pump chambers, which in turn drives the fluid through the pump in one direction. Genetic algorithms along with artificial neural networks are used for optimizing the pump geometry and the actuation frequency. A simple example with moving walls is considered for validation by developing an exact analytical solution of the Navier–Stokes equation and comparing it with numerical simulations. Possible applications of these pumps are in microelectronics cooling and drug delivery. Based on the results obtained from the fluid–structure interaction analysis, three optimized geometries result in flow rates that match the predicted flow rates with 95% accuracy. These geometries need further investigation for fabrication and manufacturing issues.

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