Darlington Amadi
EMMS drag model is as follows:
The EMMS drag model is based on the work of Chen et al. (2009) and can be expressed as:
$$F_D = \frac{1}{8} \pi d_p^2 \rho_c C_D |u_c - u_p| (u_c - u_p)$$
Where:
- $F_D$ is the drag force per unit volume of the dispersed phase
- $d_p$ is the particle diameter
- $\rho_c$ is the density of the continuous phase
- $C_D$ is the drag coefficient
- $u_c$ is the velocity of the continuous phase
- $u_p$ is the velocity of the dispersed phase
The drag coefficient, $C_D$, is calculated using the following expression:
$$C_D = \frac{24}{\alpha_c^{0.65}Re_p} (1 + 0.15 \alpha_c^{-0.687} Re_p^{0.687})$$
Where:
- $\alpha_c$ is the volume fraction of the continuous phase
- $Re_p$ is the particle Reynolds number, defined as:
$$Re_p = \frac{\rho_c d_p |u_c - u_p|}{\mu_c}$$
- $\mu_c$ is the dynamic viscosity of the continuous phase
The C++ code implementation of the EMMS drag model in ANSYS Fluent 2023 would be similar to the following:
```cpp
// Calculate the particle Reynolds number
double ReP = rho_c * dp * fabs(u_c - u_p) / mu_c;
// Calculate the drag coefficient
double alpha_c = 1.0 - alpha_p; // Volume fraction of continuous phase
double CD = 24.0 / (pow(alpha_c, 0.65) * ReP) * (1.0 + 0.15 * pow(alpha_c, -0.687) * pow(ReP, 0.687));
// Calculate the drag force
double FD = 0.125 * M_PI * dp * dp * rho_c * CD * fabs(u_c - u_p) * (u_c - u_p);
```
Good luck. partial credit AI
Unfortunately, the EMMS (Easy Multiphase Musliphase Model) drag model isn't a built-in feature within ANSYS Fluent. It requires implementation through a User-Defined Function (UDF). There's no official ANSYS documentation providing the exact mathematical formulae and C++ code for the EMMS drag model.
However, there are resources available online that discuss the EMMS model and potentially offer UDF code implementations. Here's what you can explore:
Here are some additional points to keep in mind:
- UDF implementation requires C++ programming knowledge and familiarity with ANSYS Fluent's UDF capabilities.
- Implementing a robust and validated UDF can be time-consuming.
- Ensure proper verification and validation of any UDF code you use before relying on its results in your simulations.
If you're not comfortable with UDF development, consider reaching out to CFD experts who can assist or suggest alternative approaches for your specific simulation needs.
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