Function oblate_to_cart_velocity

examples/pde/bhrt.cpp:330–357

* @brief Transform the velocity vectors from oblate to cartesian coordinates * * @param vel * @param pos * @return af::array */

 * @return af::array
 */
af::array oblate_to_cart_velocity(const af::array& vel, const af::array& pos) {
    if (vel.dims() != pos.dims())
        throw make_error("Arrays must have the same dimensions");
    else if (pos.dims()[0] != 3)
        throw make_error("Arrays must have 3 principal coordintes");

    af::array r = pos(0, af::span);
    af::array o = pos(1, af::span);
    af::array p = pos(2, af::span);

    af::array ur = vel(0, af::span);
    af::array uo = vel(1, af::span);
    af::array up = vel(2, af::span);

    double a     = J / M;
    af::array ra = af::sqrt(r * r + a * a);

    af::array ux =
        (ur * r * af::sin(o) / ra + uo * ra * af::cos(o)) * af::cos(p) -
        up * r * af::sin(o) * af::sin(p);
    af::array uy =
        (ur * r * af::sin(o) / ra + uo * ra * af::cos(o)) * af::sin(p) +
        up * r * af::sin(o) * af::cos(p);
    af::array uz              = ur * af::cos(o) - uo * r * af::sin(o);
    af::array transformed_vel = af::join(0, ux, uy, uz);

    return transformed_vel;
}

/**
 * @brief Transform the velocity vectors from cartesian to oblate coordinates