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July 17, 1998, 17:23 |
compressible channel flow..
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#1 |
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Hi there ,
I am developing a code to study compressible - convection in channel-flow.. As a validation check I wanted to see if as a limiting case I can obtain the fully developed velocity profiles including the 'developing flow ' profiles at the entrance. I am faced with the following problems: 1. for random initial conditions for the velocity (transverse component suppressed) the flow does evolve to a smooth profile ..but remains in the developing phase. I used a linear density profile to start with. I had scaled my time with respect to the sound crossing time. Thinking that I was not allowing sufficient time for the flow to develop ( and length as well) I changed my time and length scaling ( L ..w.r.t channel length ..not width ..as done earlier; and time w.r.t the L/(peak velocity)) 2. the flow does evolve this time ..but does not quite converge . ( I use the sum_{i,j}(v_{n} - v{n-1}) to check for convergence....any better way ..?) Instead the convergence is destroyed by something like a 'boundary - disturbance' emanating from the outlet. My understanding : since I did start without bothering about the intial flow being 'divergence less' or not...there might be the possibility of 'incoming 'waves from the outlet..destroying the solution. I must add that I had left the outlet boundary to evolve by itself.. ( is this wrong..?) Now ..if I carefully choose a div.V = 0 intial state and put the velocity - profile by hand at the outlet ( fix it I mean ..) and start with a flat - profile at the inlet (fixed) .....Can I expect to capture what I intended to get ..viz..all the stages of a developing flow..in a channel.? Does the div.V =0 state eliminate the 'waves' ? ( how do I know if these are 'numerical' or 'real' waves..?) any suggestions..? thanks Prabhu |
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