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Waqar Amin
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I was asked a question that the Reynold number of a fluid is greater than 4000 but flow Is Still laminar. How is it possible? can anyone explain?.
HengHY said:what kind of fluid?
He also observed the lower limit of Re =2.3 x 103 for large distances down the pipe.
The Reynold number is a dimensionless quantity used to determine the type of flow (laminar or turbulent) in a fluid based on its velocity, density, and viscosity. It is important in fluid dynamics because it helps predict the behavior of fluids in different situations, such as in pipes, pumps, and aerodynamics.
A Reynold number of 4000 is considered the critical point for the transition between laminar and turbulent flow in a fluid. Below 4000, the flow is typically laminar (smooth and predictable), while above 4000, the flow becomes turbulent (chaotic and unpredictable).
The Reynold number, denoted as Re, is calculated by multiplying the fluid velocity (v) by its characteristic length (L) and dividing by its kinematic viscosity (ν), which is a measure of its resistance to flow. The units of the Reynold number are dimensionless, as all units cancel out in the calculation.
No, a fluid can only have one type of flow at a given Reynold number. However, as the Reynold number is affected by the fluid's velocity, density, and viscosity, changes in these parameters can cause the Reynold number to fall below or rise above 4000, resulting in a transition between laminar and turbulent flow.
The Reynold number plays a significant role in determining the drag force on an object moving through a fluid. At low Reynold numbers, the drag force is primarily due to the fluid's viscosity and is therefore higher in laminar flow. At high Reynold numbers, the drag force is mainly caused by the turbulence in the fluid, resulting in a higher drag force in turbulent flow.