免费弗劳德数计算器
计算明渠流的弗劳德数，判断急流或缓流。
Froude Number
0.957990
Froude Number vs Flow Velocity
公式
## Froude Number The Froude number characterises the ratio of flow inertia to gravitational effects in open-channel flow. ### Formula **Fr = v / sqrt(g d)** - *v* = mean flow velocity - *g* = gravitational acceleration - *d* = hydraulic depth (cross-section area divided by top width) Fr < 1: subcritical (tranquil). Fr = 1: critical. Fr > 1: supercritical (rapid).
计算示例
River at 3 m/s with 1 m depth.
- 01Fr = v / sqrt(g d)
- 02Fr = 3 / sqrt(9.807 * 1)
- 03Fr = 3 / 3.131
- 04Fr = 0.958 (subcritical, but nearly critical)
常见问题
What is the physical meaning of the Froude number?
It compares the speed of the flow to the speed of surface gravity waves. When Fr > 1, flow moves faster than waves can propagate upstream, so upstream conditions cannot influence downstream.
How does the Froude number relate to ship design?
For ships, the Froude number (based on hull length) determines wave-making resistance. Ships are most efficient below the hull speed, roughly Fr = 0.4.
What happens at Fr = 1?
Critical flow, with minimum specific energy for a given discharge. This condition is used in weir design to measure flow rates.
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