The KeuleganâCarpenter number is important for the computation of the wave forces on offshore platforms. |
In fluid dynamics, the KeuleganâCarpenter number, also called the period number, is a dimensionless quantity describing the relative importance of the drag forces over inertia forces for bluff objects in an oscillatory fluid flow. Or similarly, for objects that oscillate in a fluid at rest. For small KeuleganâCarpenter number inertia dominates, while for large numbers the ( turbulence) drag forces are important.
The KeuleganâCarpenter number KC is defined as: [1]
where:
The KeuleganâCarpenter number is named after Garbis H. Keulegan (1890â1989) and Lloyd H. Carpenter.
A closely related parameter, also often used for sediment transport under water waves, is the displacement parameter ÎŽ: [1]
with A the excursion amplitude of fluid particles in oscillatory flow and L a characteristic diameter of the sediment material. For sinusoidal motion of the fluid, A is related to V and T as A = VT/(2Ï), and:
The KeuleganâCarpenter number can be directly related to the NavierâStokes equations, by looking at characteristic scales for the acceleration terms:
Dividing these two acceleration scales gives the KeuleganâCarpenter number.
A somewhat similar parameter is the Strouhal number, in form equal to the reciprocal of the KeuleganâCarpenter number. The Strouhal number gives the vortex shedding frequency resulting from placing an object in a steady flow, so it describes the flow unsteadiness as a result of an instability of the flow downstream of the object. Conversely, the KeuleganâCarpenter number is related to the oscillation frequency of an unsteady flow into which the object is placed.
The KeuleganâCarpenter number is important for the computation of the wave forces on offshore platforms. |
In fluid dynamics, the KeuleganâCarpenter number, also called the period number, is a dimensionless quantity describing the relative importance of the drag forces over inertia forces for bluff objects in an oscillatory fluid flow. Or similarly, for objects that oscillate in a fluid at rest. For small KeuleganâCarpenter number inertia dominates, while for large numbers the ( turbulence) drag forces are important.
The KeuleganâCarpenter number KC is defined as: [1]
where:
The KeuleganâCarpenter number is named after Garbis H. Keulegan (1890â1989) and Lloyd H. Carpenter.
A closely related parameter, also often used for sediment transport under water waves, is the displacement parameter ÎŽ: [1]
with A the excursion amplitude of fluid particles in oscillatory flow and L a characteristic diameter of the sediment material. For sinusoidal motion of the fluid, A is related to V and T as A = VT/(2Ï), and:
The KeuleganâCarpenter number can be directly related to the NavierâStokes equations, by looking at characteristic scales for the acceleration terms:
Dividing these two acceleration scales gives the KeuleganâCarpenter number.
A somewhat similar parameter is the Strouhal number, in form equal to the reciprocal of the KeuleganâCarpenter number. The Strouhal number gives the vortex shedding frequency resulting from placing an object in a steady flow, so it describes the flow unsteadiness as a result of an instability of the flow downstream of the object. Conversely, the KeuleganâCarpenter number is related to the oscillation frequency of an unsteady flow into which the object is placed.