[ajayjatoliya]

Hello REEF 3D Team,

I have a query regarding reduced NWT. As the author mentioned in this paper (https://doi.org/10.1016/j.coastaleng.2021.104002), they use reduced NWT for the generation of waves. The dimension of the NWT mentioned in the paper is 4.4x2.0x0.7, whereas the wavelength is 8.8 m. As mentioned in the CFD tutorials 9.6 and 9.7, the length of the wave generation and wave absorption should be one and two times of the wavelength respectively. could you please help me how to solve the problem for generating wave in NWT?

[valgrinda]

It depends on what you need. Reducing the NWT length is possible using active generation and absorption. Then the wave will pass through the domain. We have successfully used this for long waves and sediment transport. In case you are interested in good quality waves though and want to capture the wave transformation and hydrodynamics, a longer tank will be better.

[ajayjatoliya]

Thank you sir for your reply,

I am solving the sediment transport problem due to the waves. For reduced NWT, I tried with Dirichlet wave generation (DWG) and Active wave absorption (AWA) using B 98 3 and B 99 3, but the waves were not generated properly. I have attached my control and ctrl file, Could you please suggest me, what parameter I need to change?

thank you sir

## Control
C 11 6
C 12 3
C 13 3
C 14 7
C 15 21
C 16 3

B 1 0.05

B 10 0.0 4.4 0.0 2.0 0.0 0.7

M 20 2

M 10 14


## Ctrl

B 10 1
B 50 0.0001
B 90 1
B 92 4
B 91 0.12 8.8
B 98 3
B 99 3

D 10 4
D 20 2
D 30 1

F 30 3
F 40 3
F 42 1.0
F 60 0.40

I 12 1

N 40 3
N 41 60.0
N 47 0.25

M 10 14

P 10 1
P 30 0.1
P 40 1
P 42 1.0

T 10 0

W 22 -9.81

P 52 0.0125
P 53 1
P 55 0.50

P 51 2.50 0.0125
P 51 5.00 0.0125
P 51 15.0 0.0125
P 51 20.0 0.0125

[valgrinda]

You are not using the correct wave theory for the given wave parameters. Try 5th-order cnoidal waves. Also extend the wave tank height to 0.8 or 0.9 m.

Since your waves are quite non-linear, AWA doesn't work perfectly. Best to use B 98 4, so that you also have AWA on the wave generation side. Otherwise the reflections build up quite a bit.

[ajayjatoliya]

Thank you, sir,

I am trying to solve the sediment transport problem using the waves-only condition. In the paper I mentioned above, the author used the 2nd-order Stoke waves theory. I am trying to replicate that.
I also use the B 98 4 parameter, but unable to solve the problem
Thank you sir

[valgrinda]

It works with 5th order cnoidal waves.

[ajayjatoliya]

Thank you sir your reply

In this paper (https://doi.org/10.1016/j.coastaleng.2021.104002) the author mentions that they have used 2nd order stoke wave for reduced NWT.