Turbulent flow velocity profiles

In summary, the conversation discusses a question given by a lecturer regarding turbulent flow and velocity profiles in ducts and pipes. The question asks for the velocity profiles of air and water in specific diameters and Reynolds numbers, as well as calculations for vmean and vy=0. Additionally, the Blasius equation is mentioned and the need to find the kinematic viscosity from textbooks or online resources.
  • #1
suvernfraggle
3
0
i've been given this question by my lecturer at university and I am struggling with where to start with it to be honest. it feels like i don't have enough information. please can someone help?

For turbulent flow, the velocity profile inside a duct and a pipe of diameters Dd and Dp and
both with distance y from the centre line is: vy/vy=0 = (1-y/r)1/7, where vy=0 = vmean/0.817 and vmean=Q/A. Plot the velocity profiles for:

(a) Air flowing in a duct measuring Dd = 0.6m and with Re = 105.
(b) Water flowing in a pipe measuring Dp = 0.5m and with Re = 105.
(c) Calculate the vmean and vy=0 for both cases (a) and (b)
(d) If the Blasius equation f = 0.079Re-0.25 applies, calculate the values of f and ΔP/L for (a)
 
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  • #2

1. What is turbulent flow velocity profile?

Turbulent flow velocity profile refers to the variation of fluid velocity across a cross-section of a turbulent flow. In turbulent flow, the fluid particles move in a chaotic manner, resulting in a constantly changing velocity profile.

2. What factors affect turbulent flow velocity profiles?

The factors that affect turbulent flow velocity profiles include the fluid properties, flow rate, and the geometry of the flow system. Other factors such as surface roughness and external disturbances can also influence the velocity profile.

3. How is turbulent flow velocity profile measured?

Turbulent flow velocity profile can be measured using techniques such as hot-wire anemometry, laser Doppler anemometry, and particle image velocimetry. These techniques involve using specialized instruments to record the velocity at different points in the flow.

4. What is the significance of turbulent flow velocity profiles?

Turbulent flow velocity profiles play a crucial role in understanding and predicting the behavior of turbulent flows. The velocity profile affects parameters such as pressure drop, heat transfer, and mixing, which are important in various engineering applications.

5. How can turbulent flow velocity profiles be controlled?

Controlling turbulent flow velocity profiles can be achieved by changing the flow rate, altering the geometry of the flow system, or using flow control devices such as baffles and flow straighteners. Additionally, reducing surface roughness and minimizing external disturbances can also help to control the velocity profile.

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