A Bidirectional Valveless Piezoelectric Micropump With Double Chambers Applying Synthetic Jet

2015 ◽  
Author(s):  
Xitong Zhang ◽  
Song Yang ◽  
Xiuhua He ◽  
Shouqi Yuan
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Flow Field ◽  
Simple Structure ◽  
Piezoelectric Actuators ◽  
Reynolds Numbers ◽  
Synthetic Jet ◽  
Volume Changes ◽  
Sinusoidal Vibration ◽  
Sst Turbulence Model

A novel bidirectional valveless piezoelectric micropump with double chambers applying synthetic jet effect was developed. The numerical simulation was applied to study the performance and flow field of the micropump. The micropump consisted of a pump body, a cover and two piezoelectric actuators had a simple structure. The direction of the flow of the micropump could change immediately based on the Coanda effect by controlling the displacement of the two piezoelectric actuators. And the synthetic jet element increase the flowrate greatly. The effects of the Reynolds number and frequency on the flowrate were studied. The size of the throat was 200 μm × 200 μm. The Reynolds numbers were 500 and 1000 in the simulation and the SST turbulence model was chosen. The sinusoidal vibration was applied and the frequency ranged from 10 to 50 Hz. The results showed that the flowrate of jet entrainment accounted for more than 80% of the outlet flowrate. And the outlet flowrates were much larger than the volume changes of the pump chambers. The fluctuation of flowrate decreased with the increase of frequency. The micropump could achieve continuous outflow as the frequency was higher than 30 Hz.

scholarly journals Numerical study of gas dynamics and heat transfer in matrix channels at various rib angles

2021 ◽  
Vol 2057 (1) ◽  
pp. 012026
Author(s):  
A V Barsukov ◽  
V V Terekhov ◽  
V I Terekhov
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Gas Dynamics ◽  
Average Velocity ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Separation Flow ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Abstract The results of numerical simulation of the separation flow in matrix channels by the RANS method are presented. The simulation is performed at the Reynolds number Re = 12600, determined by the mass-average velocity and the height of the channel. The distribution of the local Nusselt number is obtained for various Reynolds numbers in the range of 5÷15⋅103 and several rib angles. It is shown that the temperature distribution on the surface is highly nonuniform; in particular, the maximum heat transfer value is observed near the upper edge facets, in the vicinity of which the greatest velocity gradient is observed.

scholarly journals Numerical simulation and experimental research of cavitation nozzle based on equation curve

2021 ◽  
Author(s):  
Lifu Wang ◽  
Dongyan Shi ◽  
Zhixun Yang ◽  
Guangliang Li ◽  
Chunlong Ma ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Flow Field ◽  
High Speed ◽  
Quadratic Equation ◽  
Outer Contour ◽  
Study Results ◽  
Fluent Software ◽  
The Impact ◽  
Better Than

Abstract To further investigate and improve the cleaning ability of the cavitation nozzle, this paper proposes a new model that is based on the Helmholtz nozzle and with the quadratic equation curve as the outer contour of the cavitation chamber. First, the numerical simulation of the flow field in the nozzle chamber was conducted using FLUENT software to analyze and compare the impact of the curve parameters and Reynolds number on the cleaning effect. Next, the flow field was captured by a high-speed camera in order to study the cavitation cycle and evolution process. Then, experiments were performed to compare the cleaning effect of the new nozzle with that of the Helmholtz nozzle. The study results demonstrate that effective cavitation does not occur when the diameter of the cavitation chamber is too large. For the new nozzle, with the increase of the Reynolds number, the degree of cavitation in the chamber first increases and then decreases; the cleaning effect is much better than that of a traditional Helmholtz nozzle under the same conditions; the nozzle has the best cleaning effect for the stand-off distance of 300 mm.

scholarly journals Direct Numerical Simulation in Two Dimensional Homogeneous Isotropic Turbulence Using Spectral Method

2013 ◽  
Vol 5 (3) ◽  
pp. 435-445
Author(s):  
M. S. I. Mallik ◽  
M. A. Uddin ◽  
M. A. Rahman
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Flow Field ◽  
Direct Numerical Simulation ◽  
Spectral Method ◽  
Isotropic Turbulence ◽  
Qualitative Behavior ◽  
Two Dimensional ◽  
Homogeneous Isotropic Turbulence ◽  
Decaying Turbulence

Direct numerical simulation (DNS) in two-dimensional homogeneous isotropic turbulence is performed by using the Spectral method at a Reynolds number Re = 1000 on a uniformly distributed grid points. The Reynolds number is low enough that the computational grid is capable of resolving all the possible turbulent scales. The statistical properties in the computed flow field show a good agreement with the qualitative behavior of decaying turbulence. The behavior of the flow structures in the computed flow field also follow the classical idea of the fluid flow in turbulence. Keywords: Direct numerical simulation, Isotropic turbulence, Spectral method. © 2013 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. doi:http://dx.doi.org/10.3329/jsr.v5i3.12665 J. Sci. Res. 5 (3), 435-445 (2013)  

Numerical Simulation of Vortex Shedding From a Circular Cylinder in the Presence of a Free Surface

2003 ◽  
Author(s):  
S. Nagaya ◽  
R. E. Baddour
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Free Surface ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Fluid Flows ◽  
Reynolds Numbers ◽  
Cfd Simulations ◽  
Induced Drag

CFD simulations of crossflows around a 2-D circular cylinder and the resulting vortex shedding from the cylinder are conducted in the present study. The capability of the CFD solver for vortex shedding simulation from a circular cylinder is validated in terms of the induced drag and lifting forces and associated Strouhal numbers computations. The validations are done for uniform horizontal fluid flows at various Reynolds numbers in the range 103 to 5×105. Crossflows around the circular cylinder beneath a free surface are also simulated in order to investigate the characteristics of the interaction between vortex shedding and a free surface at Reynolds number 5×105. The influence of the presence of the free surface on the vortex shedding due to the cylinder is discussed.

scholarly journals Aerodynamics of Flapping Wing at Low Reynolds Numbers: Force Measurement and Flow Visualization

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Abhijit Banerjee ◽  
Saurav K. Ghosh ◽  
Debopam Das
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Flow Visualization ◽  
Force Measurement ◽  
Reynolds Numbers ◽  
Flapping Flight ◽  
Water Tank ◽  
Cross Sectional ◽  
Piv Measurement ◽  
The Difference

Flow field of a butterfly mimicking flapping model with plan form of various shapes and butterfly-shaped wings is studied. The nature of the unsteady flow and embedded vortical structures are obtained at chord cross-sectional plane of the scaled wings to understand the dynamics of insect flapping flight. Flow visualization and PIV experiments are carried out for the better understanding of the flow field. The model being studied has a single degree of freedom of flapping. The wing flexibility adds another degree to a certain extent introducing feathering effect in the kinematics. The mechanisms that produce high lift and considerable thrust during the flapping motion are identified. The effect of the Reynolds number on the flapping flight is studied by varying the wing size and the flapping frequency. Force measurements are carried out to study the variations of lift forces in the Reynolds number (Re) range of 3000 to 7000. Force experiments are conducted both at zero and finite forward velocity in a wind tunnel. Flow visualization as well as PIV measurement is conducted only at zero forward velocity in a stagnant water tank and in air, respectively. The aim here is to measure the aerodynamic lift force and visualize the flow field and notice the difference with different Reynolds number (Re), and flapping frequency (f), and advance ratios (J=U∞/2ϕfR).

Numerical Simulation of the Flow Field in Safety Valve

2012 ◽  
Vol 472-475 ◽  
pp. 1432-1436
Author(s):  
Xiao Bin Ji ◽  
Xue Yi Qi ◽  
Xiao Yan Li ◽  
Wan Bin Jin
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Flow Field ◽  
Field Distribution ◽  
Safety Valve ◽  
Structural Parameters ◽  
Flow Noise ◽  
Simulating Calculation

By using the Reynolds stress turbulence model at big Reynolds number condition and computational fluid dynamics, the data simulating calculation was carried out to the safety valve inner flow field with different opening size and different valve structural parameters. The result were showed in visual graphics , and the study showed that the valve structural parameters impact on the flow field distribution , the cavitation creation and the flow noise greatly.

Force on a Small Particle Attached to a Plane Wall in a Hiemenz Straining Flow

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
A. B. Maynard ◽  
J. S. Marshall
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Reynolds Numbers ◽  
Lower Surface ◽  
Ring Structure ◽  
Plane Wall ◽  
Small Reynolds Numbers ◽  
Particle Force ◽  
Volume Method ◽  
Excellent Accuracy

The force acting on a spherical particle fixed to a wall and immersed in an axisymmetric straining flow is examined for small Reynolds numbers. The steady, incompressible flow field is computed using an axisymmetric finite-volume method over conditions spanning five decades in the Reynolds number. The flow is characterized by the formation of a vortex ring structure in the wedge region formed between the particle lower surface and the plane wall. A power law expression for the dimensionless particle force is obtained as a function of the Reynolds number, which is found to hold with excellent accuracy for Reynolds numbers below about 0.1.

Numerical Investigation on Visualizations of Confined Air Flow in a Slot Jet Inside a Rectangular Channel

2015 ◽  
Vol 813-814 ◽  
pp. 736-741
Author(s):  
M. Muthukannan ◽  
P. Rajesh Kanna ◽  
S. Jeyakumar ◽  
J.Y. Raja Shangaravel ◽  
S. Raghu ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Numerical Investigation ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Vortex Center ◽  
Computational Domain ◽  
Reattachment Length ◽  
Aspect Ratios ◽  
Air Jet

In the present numerical investigation, the flow field of confined slot air jet in a rectangular computational domain is reported. In the present work the flow field parameters like reattachment length, vortex center and horizontal velocity profiles for various Reynolds numbers and for various aspect ratios are presented .The present study reveals that the vortex centers are moving in a downstream direction with increase in Reynolds number. The reattachment length is directly dependent on the Reynolds numbers. In case of vortex dynamics, the vortex size is indirectly dependent on the inlet jet width. In the present investigation, SIMPLE algorithm is used to solve the governing equations. It is concluded that the aspect ratio and the Reynolds number are playing dominant roles in flow field of the present computational domain.

Transitory Behavior of Synthetic Jets

2005 ◽  
Author(s):  
Michael Amitay ◽  
Florine Cannelle
Keyword(s):  
Reynolds Number ◽  
Steady State ◽  
Input Signal ◽  
Mass Flux ◽  
Reynolds Numbers ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Hot Wire ◽  
Stroke Length ◽  
Zero Net Mass Flux

The transitory behavior of an isolated synthetic (zero net mass flux) jet was investigated experimentally using PIV and hot-wire anemometry. In the present work, the synthetic jet was produced over a broad range of length- and time-scales, where three formation frequencies, f = 300, 917, and 3100Hz, several stroke lengths (between 5 and 50 times the slit width) and Reynolds numbers (between 85 and 408) were tested. The transitory behavior, following the onset of the input signal, in planes along and across the slit was measured. It was found that the time it takes the synthetic jet to become fully developed depends on the stroke length, formation frequency and Reynolds number. In general, the transients consist of four stages associated with the merging of vortices in both cross-stream and spanwise planes that grow in size, which lead to the pinch off of the leading vortex before the jet reaches its steady-state.

scholarly journals Prediction of the Propeller Performance at Different Reynolds Number Regimes with RANS

2021 ◽  
Vol 9 (10) ◽  
pp. 1115
Author(s):  
João Baltazar ◽  
Douwe Rijpkema ◽  
José Falcão de Campos
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Scale Effects ◽  
Open Water ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Transition Model ◽  
Sst Turbulence Model ◽  
Propeller Performance ◽  
Selection Of

In this study, a Reynolds averaged Navier-Stokes solver is used for prediction of the propeller performance in open-water conditions at different Reynolds numbers ranging from 104 to 107. The k−ω SST turbulence model and the γ−R˜eθt correlation-based transition model are utilised and results compared for a conventional marine propeller. First, the selection of the turbulence inlet quantities for different flow regimes is discussed. Then, an analysis of the iterative and discretisation errors is made. This work is followed by an investigation of the predicted propeller flow at variable Reynolds numbers. Finally, the propeller scale-effects and the influence of the turbulence and transition models on the performance prediction are discussed. The variation of the flow regime showed an increase in thrust and decrease in torque for increasing Reynolds number. From the comparison between the turbulence model and the transition model, different flow solutions are obtained for the Reynolds numbers between 105 and 106, affecting the scale-effects prediction.

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