Fluid flow around a wind turbine blade -- help please

[t0mm02]

Homework Statement

Estimate what the Reynolds number is of the fluid flowing around the table

Relevant Equations

Reynolds number

I have to estimate the Reynolds number of the fluid flowing around a blade but I only have one detail: the length of the blade is 0.66m.
I have no idea how to do it and I got to submit the assignment in a week, I am desperate for help here.

 

[Gordianus]

It says estimate. Have you seen the blades turning?

 

[Chestermiller]

It might help if you started out by providing for us some indication of your understanding of the definition of the Reynolds number.

 

[t0mm02]

It says estimate. Have you seen the blades turning?

I haven't. That is all the information I got which I find strange

 

[t0mm02]

It might help if you started out by providing for us some indication of your understanding of the definition of the Reynolds number.

The Reynolds numbers is a parameter that helps obtain a flow pattern estimation in various fluid flow situations
The Reynolds number is mathematically defined as:

where:

• is the fluid density (kg/m3)
• is the flow velocity
• is a linear dimension
• is dynamic viscosity (Pa.s)
• v is kinematic viscosity (m2/s)

 

[Chestermiller]

The Reynolds numbers is a parameter that helps obtain a flow pattern estimation in various fluid flow situations
The Reynolds number is mathematically defined as:
View attachment 274953
where:

• is the fluid density (kg/m3)
• is the flow velocity
• is a linear dimension
• is dynamic viscosity (Pa.s)
• v is kinematic viscosity (m2/s)

Good. I assume you are dealing with air at approximately room temperature conditions. So you know the density and viscosity, right? You also have a characteristic length. Ok so far?

 

[t0mm02]

Good. I assume you are dealing with air at approximately room temperature conditions. So you know the density and viscosity, right? You also have a characteristic length. Ok so far?

The wind turbine is supposed to be an offshore wind turbine so I am guessing the density of the air= 1,225 kg/m^3 and viscosity of air= 1,789x10^-5 (this is only what I am guessing though, doesn't mean it is right. The only known detail I know as it is visible on the imagen I posted on my post is the wind turbine geometric but I also believe that 660,60mm is too little measurement for a wind turbine blade.

 

[t0mm02]

Good. I assume you are dealing with air at approximately room temperature conditions. So you know the density and viscosity, right? You also have a characteristic length. Ok so far?

I also got the Area of the blade if it helps.

 

[Chestermiller]

The wind turbine is supposed to be an offshore wind turbine so I am guessing the density of the air= 1,225 kg/m^3 and viscosity of air= 1,789x10^-5 (this is only what I am guessing though, doesn't mean it is right. The only known detail I know as it is visible on the imagen I posted on my post is the wind turbine geometric but I also believe that 660,60mm is too little measurement for a wind turbine blade.

I’m not so sure that 0.66 m is short for a turbine blade. Why don’t you make a graph of Re vs velocity?

 

[t0mm02]

I’m not so sure that 0.66 m is short for a turbine blade. Why don’t you make a graph of Re vs velocity?

I don't understand you. When it says "Estimate what the Reynolds number is of the fluid flowing around the blade" I am guessing I have to calculate it using a formula.

 

[Chestermiller]

I don't understand you. When it says "Estimate what the Reynolds number is of the fluid flowing around the blade" I am guessing I have to calculate it using a formula.

You have the formula. Just substitute a selection of values for the velocity and plot a graph.

 

[t0mm02]

You have the formula. Just substitute a selection of values for the velocity and plot a graph.

Apparently, my teacher has just told me I have to use the typical fluid velocity, that I have no idea what it is

 

[Chestermiller]

Apparently, my teacher has just told me I have to use the typical fluid velocity, that I have no idea what it is

What does your gut tell you about the probable range of velocity values?

 

[t0mm02]

What does your gut tell you about the probable range of velocity values?

My gut? I don't understand the problem and neither I understand what my teacher has said, so I don't think my gut is able to tell me anything.

 

[berkeman]

The wind turbine is supposed to be an offshore wind turbine

Apparently, my teacher has just told me I have to use the typical fluid velocity, that I have no idea what it is

I don't understand the problem and neither I understand what my teacher has said, so I don't think my gut is able to tell me anything.

What are typical wind speeds for offshore wind installations (Google should be able to find it)? What would a typical speed be for a wind turbine of this size in those wind conditions? Google should be able to help you find ballpark numbers for that as well...

 

[Chestermiller]

What is the speed of typical winds on a moderately windy day? What about in a moderate tropical storm?

 

[Chestermiller]

I'm thinking wind speeds of 3-30 m/s, with a typical moderate value being on the order of 10 m/s. Anyway, that's my gut feeling.