Hello, everyone.
Can I ask you a question about specific heat Cp?
When I want to use isothermal wall surfaces I find that Cp confuses me a bit as I am using dimensionless to flow parameters and I don’t understand how Cp should be expressed, for example it is 1005 in room temperature air but this has units.
Here are my incoming flow parameter settings that I referenced for this condition.
[constants]
M = 2.25
gamma = 1.4
Pr = 0.72
rhoin = 1.0
uin = 1.0
vin = 0.0
win = 0.0
pin = 0.14109347442680775
mu = 4e-05
cpTref = 0.4938271604938272
cpTs = 0.19897797675575454
; cp = 1005 ; J/(kg-K)
; Tw = 322 ; k
[soln-bcs-wall]
type = no-slp-isot-wall
cpTw = cp * Tw
It is worth mentioning that cpTref and cpTs I calculated by using the following equations, with 110 and 273 as the reference temperature constants.
gamma = 1.4
p = 0.14109347442680775
rho = 1
cpTref = gamma/(gamma-1) * p / rho
cpTs = cp_Tref * 110/273
Not sure if I understand cpTref and cpTs incorrectly and how cp should be calculated?
Thank you all very much for your valuable time.
Regards, Wgbb.
That’s the (mostly) correct way to define cpTref and cpTs. We use cpT since for constant cp it’s the non-dimensional form of temperature (it’s the enthalpy), whereas temperature itself is dimensional and dependent on the units of R. However, Sutherland’s law is inherently dimensional as it’s a nonlinear relation of the temperature to the Sutherland temperature, so there is a need for a reference physical temperature that cpTref and cpTs correspond to, where the reference temperature is your freestream temperature (since the enthalpy quantity h = cpTref = gamma/(gamma-1) * p / rho you compute corresponds to your freestream enthalpy). However, it seems like your freestream temperature for your problem is 169.44, not 273, so you then need to compute cpTs in terms of this as cpTs = cpTref * Ts/Tref = cpTref * 110/169.44. You can compute your wall enthalpy in the same way as cpTw = cpTref * Twall/Tref = cpTref * 322/169.44.
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Thank you very much for your help.
Firstly apologising for my misunderstanding.
I think the entropy filtering algorithm is very good to capture strong excitations effectively.
Again, thank you for your answers.
Regards, Wgbb.
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