Plot Sectional Force Distribution

Contents

Plot Sectional Force Distribution#

This example demonstrates how to extract the sectional force distribution from a completed case and report it as a dimensional quantity: the cumulative drag build-up along the X axis and the spanwise load distribution along the Y axis. The solver writes these distributions as coefficients, which are scaled by the dynamic pressure and reference area (q * A) to recover dimensional values.

import flow360 as fl

case = fl.Case.from_cloud(case_id="your-case-id")

# reference values to dimensionalize the coefficients (F = C * q * A)
density = case.params.operating_condition.thermal_state.density
reference_velocity = case.params.reference_velocity
reference_area = case.params.reference_geometry.area
force_scale = (0.5 * density * reference_velocity**2 * reference_area).to(fl.u.N)

# cumulative drag force (N) along X: the cumulative curve is an integrated
# coefficient, so C * q * A is a force.
x_dist = case.results.x_slicing_force_distribution
x_dist.wait()  # sectional post-processing can finish after the case
df_x = x_dist.as_dataframe()
df_x["Drag [N]"] = df_x["totalCumulative_CD_Curve"] * force_scale.value
df_x.plot(x="X", y="Drag [N]", title="Cumulative drag along X")

# spanwise lift loading (N/m) along Y: CFz_per_span is a per-span coefficient,
# so C * q * A is a force per unit span, not a total force.
y_dist = case.results.y_slicing_force_distribution
y_dist.wait()
df_y = y_dist.as_dataframe()
df_y["Lift [N/m]"] = df_y["totalCFz_per_span"] * force_scale.value
df_y.plot(x="Y", y="Lift [N/m]", title="Spanwise lift loading along Y")
../../_images/sectional_force_distribution.png

Example output: the dimensional cumulative drag along X and the spanwise lift loading along Y.#

Notes#

  • Use Case.from_cloud(case_id="...") to retrieve a completed case from the cloud.

  • x_slicing_force_distribution gives the cumulative drag coefficient along X; y_slicing_force_distribution gives the per-span force and moment coefficients along Y.

  • The raw distributions are non-dimensional. Multiply by q * A (with q = 0.5 * density * reference_velocity**2 and A = reference_geometry.area) to dimensionalize, following the same scaling as Calculate Dimensional Forces.

  • Mind the difference in what each distribution represents. totalCumulative_CD_Curve is an integrated (cumulative) drag coefficient, so scaling it gives a force in Newtons. totalCFz_per_span is a per-span coefficient, so scaling it gives a sectional loading (force per unit span, N/m), not a total force.

  • Sectional distributions are produced by post-processing, which can finish after the case has converged. Call wait() before reading the data.

  • filter(include="...") and filter(exclude="...") restrict the distribution to a subset of surfaces (both support wildcard patterns such as "*Wing*" and explicit surface names).

  • The X distribution column is totalCumulative_CD_Curve; the Y distribution columns are totalCFx_per_span, totalCFz_per_span and totalCMy_per_span.

Contents