Page History

4/11/2008

Optimum mesh. Decided to solve the turbulence viscous layer by refining the mesh until we get yplus less than 5 at the wall. (cell of about 30,000 is good enough to resolve the layer)

Decided on the single bend. Use h = 1.5w and compare with h = 1w
w = baffle spacing

For h = 1.5:
Get Pressure coefficient loss of 3 across the bend
Lots of stagnant flow at the bottom corner
Yplus at wall less than 5

For h = 1;
Pressure coefficient loss of 3.21 across the bend
Yplus less than 5

Explanations:
Lower h has higher pressure coefficient loss. The fluid need to flow through constricted region which increase the frictional losses as compared with the flow through bigger h?

Evaluate the current progress
1. Model and validate a simple 180 degree turn over two baffles:

Create fully second order accurate model (done)

Perform mesh sensitivity analysis (using coarse, medium and fine meshes) (done)

Model the baffles using alternate Turbulence models (K-e Standard, K-e Realizable, K-w)

Analyze the effects of changing the baffle clearance height (done. increase height = decrease in pressure drop)

Understand and analyze the relationship between Strain Rate, Energy Dissipation and Kinematic Viscosity

Create a flexible mesh that uses parametrization to easily change geometry dimensions

Analyze the effect of the Reynolds Number on the results

Analyze the sensitivity of the model to convergence residuals (done)

Change the velocity inlet to 0.5 m/s to check the Reynold's number effect. We see that the pressure difference is about the same delCp = 3.04;

3/7/2008
Boundary layer
first row = 0.0015
growth factor = 1.13
rows = 6
Depth = 0.0124841

Third boundary layer

first row = 0.003
growth = 1.025
rows = 4
depth = 0.0124575

3/3/2008
Create boundary layer at the wall. Assume the BL thickness is 0.012 m from the previous results.
File name: sharp bend medium boundary layer.dbs
Goal: Create 15000 elements mesh with special treatment to the mesh at the wall.
First row = 0.0005
Growth factor = 1.19
Rows = 10
Depth = 0.0123544

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