Calculating the Force of Moving Water: Vehicle Hydrodynamic Drag Equation

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SUMMARY

The discussion centers on calculating the hydrodynamic drag force experienced by a vehicle moving upstream in water. The primary equation proposed is F = Apv², where F is the force, A is the surface area of submerged parts, p is the water density, and v is the water velocity. Participants also explore the relationship between hydrodynamic and aerodynamic drag, noting that the same drag equation can be applied with adjustments for water density and specific coefficients of drag. The conversation emphasizes the importance of parameters such as water depth, speed, and density in these calculations.

PREREQUISITES
  • Understanding of hydrodynamic principles
  • Familiarity with drag equations in fluid dynamics
  • Knowledge of water density and its impact on force calculations
  • Basic physics concepts related to force and motion
NEXT STEPS
  • Research the application of the drag equation in various fluid mediums
  • Explore the differences between hydrodynamic and aerodynamic drag coefficients
  • Learn about the impact of water depth on vehicle resistance
  • Investigate computational fluid dynamics (CFD) tools for simulating vehicle performance in water
USEFUL FOR

Engineers, vehicle designers, and researchers interested in fluid dynamics, particularly those focusing on the effects of water resistance on vehicles in aquatic environments.

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Does anyone know of an equation I may use to calculate the force of moving water? I am trying to theoretically workout the resistive force a vehicle would meet if it were to drive upstream (hydrodynamic drag).

I am assuming the main parameters such an equation would include are water depth, water speed, water density and the surface area of the exposed parts of the vehicle such as the portion of its tyres submerged in the stream.

Thanks.
 
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Force=v*rate of change of mass
F=Apv^2, where p = density of water, v=velocity of water, A=surface area
 
Thank you very much, Harmony.
 
I am wondering now if it is possible to use exactly the same equation for calculating aerodynamic drag as is used for calculating hydrodynamic drag?

Instead of using a figure for air density, a figure for water density is employed. The coefficient of drag remains the same.

What do you think?

Aerodynamic drag is: F = 0.5PV²Cdf

Where:

P = air density
V = velocity
Cd = coefficient of drag
f = frontal areaEdit: Of course the coefficient of drag would be specific to the part of the vehicle subjected to the flowing water.
 

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