Calculator Inputs
Pressure Profile Plot
The graph shows pressure growth with depth along the plate. Centroid and center of pressure markers appear after calculation.
Example Data Table
| Fluid | Density (kg/m³) | Width (m) | Length (m) | Top Depth (m) | Angle (°) | Area (m²) | Centroid Depth (m) | Force (kN) | Center of Pressure (m) |
|---|---|---|---|---|---|---|---|---|---|
| Fresh Water | 1000 | 2.5 | 3.0 | 1.2 | 90 | 7.50 | 2.70 | 198.65 | 2.98 |
| Sea Water | 1025 | 1.8 | 2.4 | 0.9 | 60 | 4.32 | 1.94 | 86.45 | 2.17 |
| Light Oil | 850 | 1.5 | 2.0 | 0.7 | 75 | 3.00 | 1.67 | 41.89 | 1.85 |
Formula Used
This calculator applies hydrostatic force relations for a fully submerged rectangular plane surface in a static fluid.
Here, b is plate width, L is plate length along the surface, htop is the top edge depth, ρ is fluid density, g is gravitational acceleration, and θ is the angle with the fluid surface.
How to Use This Calculator
- Select a fluid type or enter a custom density value.
- Provide gravity, plate width, plate length, and top edge depth.
- Enter the plate angle measured from the fluid surface.
- Choose graph points, then press Calculate Fluid Force.
- Review force, pressure, center of pressure, and the pressure plot.
- Use the CSV and PDF buttons to save your result summary.
Frequently Asked Questions
1) What does this calculator measure?
It computes the hydrostatic resultant force acting on a submerged rectangular plate. It also estimates centroid depth, pressure values, and the center of pressure position.
2) Which units does the calculator use?
Inputs use SI units: meters, kilograms per cubic meter, and meters per second squared. Results are displayed in pascals, kilopascals, newtons, kilonewtons, and meters.
3) Why does the force increase with depth?
Fluid pressure rises with depth because the weight of fluid above the point becomes larger. Greater depth produces greater pressure, which increases the total hydrostatic force.
4) What is the center of pressure?
The center of pressure is the location where the resultant hydrostatic force acts. It lies below the centroid for vertical or inclined submerged surfaces because pressure grows with depth.
5) Can I use this for circular or triangular plates?
Not directly. This version is designed for rectangular plane surfaces. Other shapes need different area and centroidal moment expressions for accurate center of pressure calculations.
6) What angle should I enter?
Enter the angle between the plate and the fluid surface. A vertical plate uses 90 degrees. Smaller angles represent more gently inclined surfaces.
7) Does the calculator assume moving fluid?
No. It assumes a static fluid with no acceleration other than gravity. Dynamic effects, flow impact, and turbulence are outside this model.
8) When should I use custom density?
Use custom density when your liquid differs from the listed presets. This is useful for brines, chemical mixtures, process fluids, or temperature-adjusted density values.