Why did PySPH skip some syntax when executing Equation？

[hrbyrb]

I was trying to write a new set of constitutive equations, but when I executed the example, I found a line of code in the FintDragForce4(equation) that never executed. As shown in Figure1:

Figure 1

I checked the.hdF5 data file, in which the betaIMEC value is 0, but none of the parameters in the formula is 0, and I have executed this calculation code externally, and got its specific value 839.7, as shown in Figure 2 and 3.

Figure 2

Figure 3

Also I have added all the variables to the util file, so a betaIMEC value of 0 should not be without output.

• Has anyone had any problems like this, or can anyone offer any suggestion?

The FintDragForce4(equation) code is as follows：

class FintDragForce4(Equation):
    r"""Calculate the drag force, including the interphase momentum exchange 
        coefficient(beta_IMEC)

    """
    def __init__(self, dest, sources, rho=1000.0, nu=0.02, 
                 gx=0.0, gy=0.0, gz=0.0, dim=2):
        self.rho = rho
        self.nu = nu
        self.dim = dim
        self.gx = gx
        self.gy = gy
        self.gz = gz
        super(FintDragForce4, self).__init__(dest, sources)

    def initialize(self, d_idx, d_Fdrau, d_Fdrav, d_Fdraw, 
                   d_Fintu, d_Fintv, d_Fintw, d_betaIMEC, d_Re, d_Cdrag):
        
        d_betaIMEC[d_idx] = 0.0
        d_Re[d_idx] = 0.0
        d_Cdrag[d_idx] = 0.0
        
        d_Fdrau[d_idx] = 0.0
        d_Fdrav[d_idx] = 0.0
        d_Fdraw[d_idx] = 0.0
        
        d_Fintu[d_idx] = 0.0
        d_Fintv[d_idx] = 0.0
        d_Fintw[d_idx] = 0.0

    def loop(self, d_idx, d_u, d_v, d_w, d_Vol, d_na, d_dia,
                   d_u_javerage, d_v_javerage, d_w_javerage,
                   d_Fdrau, d_Fdrav, d_Fdraw, d_betaIMEC, 
                   d_Fintu, d_Fintv, d_Fintw, d_Re, d_Cdrag):

        tempu = (d_u_javerage[d_idx] - d_u[d_idx])
        tempv = (d_v_javerage[d_idx] - d_v[d_idx])
        tempw = (d_w_javerage[d_idx] - d_w[d_idx])
        temp = sqrt(tempu*tempu + tempv*tempv + tempw*tempw)
        na = d_na[d_idx]
        dia = d_dia[d_idx]
        Volume = d_Vol[d_idx]
               
        Cdrag = d_Cdrag[d_idx]
        
        if d_na[d_idx] <= 0.8:
            d_betaIMEC[d_idx] = 150.0 * (1-na)**2 / na * self.nu / dia**2 +\
                                1.75*(1-na) * self.rho / dia * temp
        else:
            d_Re[d_idx] = self.rho * na * dia * temp / self.nu
            if d_Re[d_idx] >= 1000.0:
                d_Cdrag[d_idx] = 0.43
            else:
                #d_Re[d_idx] = 1.0 if d_Re[d_idx] < 1.0 else d_Re[d_idx]
                d_Cdrag[d_idx] = 24*(1 + 0.15*d_Re[d_idx]**0.687)/d_Re[d_idx]
            
            d_betaIMEC[d_idx] = 0.75 * Cdrag * na*(1-na)/dia * self.rho *\
                                na**(-2.65) * temp

[prabhuramachandran]

By default not all properties you setup in a particle array are saved to disk. This is because very often there are many properties that are not useful to save on disk. The particle array's output_property_arrays attribute is used to determine which properties are saved.
Use the particle array's set_output_arrays method to specify exactly what arrays you wish to save to disk:
https://pysph.readthedocs.io/en/latest/reference/particle_array.html?#pysph.base.particle_array.ParticleArray.set_output_arrays

Alternatively, if you want to save all properties you can pass --detailed-output on the command line to save all properties. Of course, this will increase the size of your output files.

[hrbyrb]

Thank you for your reply.
I have found out the reason for the error, there is a line of code in the equation with a wrong position, resulting in the variable equal to 0.

[prabhuramachandran]

Sorry, I realize I missed that you had indeed set the output properties on the particle array. Could you clarify which line of code in your screenshot was causing the problem?

[hrbyrb]

The value of Cdrag in line 471 is passed on line 458, which should actually be placed on line 470. I have to say, it was a very embarrassing mistake, haha

[prabhuramachandran]

These sort of mistakes happen to the best of us. :)