Hello,
I’m simulating a fish passage in a 3D model. I’m using K-e to model the turbulence in the flow. According to the literature, the dissipation power criterion in a fish passage should be less than 200 W/m3 (I suppose in a 1D model).
My model runs well. However if I integrate the energy dissipation variable along my fish passage in 3D, I get an average of 900 W/m3. For the same fish passage if I calculate the energy dissipation according to the 1D model P=(rhogQ*dH)/V, I’ll get a value less than 200 W/m3.
Does anyone know if my results are typical? I suppose that the difference comes from the 1D formula that doesn’t take direcly into account the turbulence energy, which means that the 1D formula and criterion isn’t suitable for real case or for a 3D model.
Any insights would be greatly appreciated.
Thank you
Hi [name removed],
I am not familiar with expressing energy loss in power, but I guess I can interpret this that the water levels upstreams of the fish passage are much higher than your 1D model shows?
Is this fish passage realised in a series of weirs? The flow over weirs in a 1D model is often calibrated (emperically) with the help of coefficients which are dependent on the shape of the bed and the horizontal contraction. A 2D/3D model might require a high resolution to achieve similar accuracy. Could you elaborate on how your fish passage functions?
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Thank you for your message.
Yes the fish passage is a series of weirs (I attached a screenshot of the clipped bassins). The upstream levels are the same in both cases.
To add some details : Telemac 3D give me the “dissipation of turbulent kinetic energy (W/kg)” which I convert in W/m3. Then I compute the mean dissipation in a bassin.
One the other hand literature recommands a Power dissipation about 200 W/m3 (calculated with the simple formula of my last post).
So I’m wondering if there’s a way to compare both approach to calculate the dissipation of energy.
Have a nice day
Interesting! I have not looked at this parameter “dissipation of turbulent kinetic energy (W/kg)” before. It does raise the question to me if “loss of turbulent energy” (3D) is the same as “loss in potential energy”, which is what your 1D equation seems to compute. Some loss in potential energy may result into an increase in turbulent energy which further in the model will result in a loss in turbulent energy, but there are also other factors increase the turbulent energy.
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