Hydrostatic Stress Calculator Form
The form uses a 3-column layout on large screens, 2 columns on medium screens, and 1 column on mobile.
Formula Used
Gauge hydrostatic pressure: p = ρgh
Using specific weight: p = γh
Absolute pressure: pabs = patm + ρgh
Hydrostatic force on a flat area: F = pA
Hydrostatic stress tensor: σ = -pI, so σ₁ = σ₂ = σ₃ = -p
Where:
- ρ = fluid density
- γ = specific weight of the fluid
- g = gravitational acceleration
- h = depth below the free surface
- A = loaded area
- p = pressure or hydrostatic stress magnitude
How to Use This Calculator
- Choose whether you want to enter fluid density or specific weight.
- Enter gravity, fluid depth, and the area receiving the pressure.
- Set atmospheric pressure if you also want absolute stress values.
- Select the output pressure unit for the displayed results and graph.
- Click the calculate button to show the result above the form.
- Use the CSV or PDF buttons to export the computed summary.
Example Data Table
| Fluid | Density (kg/m³) | Depth (m) | Gauge Pressure (kPa) | Absolute Pressure (kPa) |
|---|---|---|---|---|
| Fresh water | 1000 | 5.0 | 49.05 | 150.38 |
| Seawater | 1025 | 20.0 | 201.11 | 302.43 |
| Mercury | 13,595 | 1.2 | 160.06 | 261.39 |
FAQs
1. What is hydrostatic stress?
Hydrostatic stress is equal normal compression acting in all directions inside a fluid at rest. Its magnitude depends on the fluid weight above the point and the chosen pressure reference.
2. Is hydrostatic stress the same as pressure?
In a stationary fluid, hydrostatic stress magnitude equals pressure. Engineers often use the terms interchangeably, while solid mechanics usually writes the stress tensor as equal compressive normal stresses.
3. What is the difference between gauge and absolute pressure?
Gauge pressure ignores atmospheric pressure and measures only the fluid column effect. Absolute pressure includes atmospheric pressure, so it is always larger than gauge pressure by the atmospheric amount.
4. Why are all principal stresses equal here?
A hydrostatic state has no directional preference. The three principal normal stresses are identical, so shear stress vanishes and the stress tensor becomes a diagonal matrix with equal entries.
5. Does container shape affect hydrostatic stress?
At a given depth in the same fluid, pressure depends on density, gravity, and depth only. Container shape changes total force distribution on walls, but not local hydrostatic stress.
6. Can I use this for gases?
Yes, but only for simple cases where density stays nearly constant over the depth considered. For large height changes, compressibility matters and a constant-density model becomes less accurate.
7. What area should I enter for force?
Enter the loaded flat area receiving the pressure value you want to apply. For surfaces where pressure changes strongly with depth, use centroid depth carefully or integrate pressure over the surface.
8. Why does the graph increase linearly with depth?
For constant density and constant gravity, hydrostatic pressure follows a linear relationship with depth. That makes the pressure gradient constant and the graph a straight rising line.