Zigzag Channel with Flow Pulsation CFD Simulation (Validation)
The simulation is based on the paper “CFD SIMULATIONS OF FLOW AND HEAT TRANSFER IN A ZIGZAG CHANNEL WITH FLOW PULSATION” and its results are compared and validated with the results in the article.
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The present problem simulates the flow of water passing through a canal in a zigzag pattern. The simulation is based on a reference paper “CFD SIMULATIONS OF FLOW AND HEAT TRANSFER IN A ZIGZAG CHANNEL WITH FLOW PULSATION” and its results are compared and validated with the results in the article.
The channel model is such that the number of stages of channel oscillation in the horizontal direction is equal to ten and the angle of the channel in each of these ten stages for modeling is assumed to be equal to 15 degrees. Several different Reynolds values, including 53, 107, 191, 266, 320, 427, and 534, were used for this simulation; Therefore, due to the low Reynolds values, the flow in all models is defined as laminar.
Therefore, the inlet velocity of water flow in different models varies based on the Reynolds value, but the inlet water flow temperature in all models is equal to 293.15 K. The lower wall of the zigzag channel is insulated and the upper wall has a constant temperature of 276.65 K. The main purpose of the problem is to investigate the amount of Nusselt number in the vicinity of the upper wall of the channel.
Zigzag Channel Geometry & Mesh
The present model is drawn in three dimensions using Design Modeler software. The present model is related to a channel that has a zigzag structure in its horizontal direction, which is equal to ten zigzag states. The angle of each of the model’s ups and downs with a horizontal direction is defined as 15 degrees. Also, the width of the channel or the vertical distance between the upper and lower walls is assumed to be equal to 8 mm and the depth of this channel is equal to 1 mm.
The following figure shows a view of the geometry.
The meshing of the model has been done using ANSYS Meshing software and the mesh type is unstructured. The element number is 144713, and a boundary layer mesh is used on the upper and lower walls of the canal.. The following figure shows the mesh.
Zigzag Channel CFD Simulation
To simulate the present model, several assumptions are considered:
- We perform a pressure-based solver.
- The simulation is steady.
- The gravity effect on the fluid is ignored.
A summary of the defining steps of the problem and its solution is given in the following table:
|gauge pressure||0 pascal|
|wall motion||stationary wall|
|heat flux||0 W.m-2|
|wall motion||stationary wall|
|Spatial discretization||pressure||second order|
|momentum||second order upwind|
|energy||second order upwind|
|gauge pressure||0 Pascal|
|x-velocity & y-velocity||variable|
At the end of the solution process, the value of the Nusselt number in different Reynolds simulations was obtained and compared with the values in the diagram in Figure 6 of the reference paper article. The desired Nusselt number is obtained using the software report on the top wall of the model, which has a constant temperature boundary condition.
Of course, in determining the Nusselt number, we must pay attention to the values in the Reference Value section of the software. For example, in this model, the Length is twice the length of the channel cross-section, and the Reference Temperature is equal to the average of the inlet and outlet temperature of the flow. The result is shown in the following figure.
Also at the end of the solution, three-dimensional velocity, pressure, and temperature contours are obtained for three different Reynolds values including 53, 266 and 534.
There are a Mesh file and a comprehensive Training Movie that presents how to solve the problem and extract all desired results.