I'm confused little, Tests on blades are, Fatigue test and static bending test.
Since blade is rotate 360 degree , how can we say that there is static component of aerodynamic on it (i.e. lift and drag)?
Generally, we try to simplify the problems so that we can predict the behavior of a 3-D real event using a 2-D model which is simpler and faster to be studied. Similarly, static tests offer less complexity than dynamic ones and can provide acceptable thresholds in many cases. Attached is an interesting paper from NREL that shows the weakness of a simplified problem for dynamic stall analysis of HAWTs.
While the aerodynamic forces on HAWT blades are changing continuously, the lift or drag forces can be calculated at a certain time period. I hope this short answer helps.
To my opinion, the term "static"in this context is a bit confusing and misleading. I agree with Ahmed: if I hear static, I would think of structural kind of testing. What in aerodynamics could be more correct, is maybe talking about "stationary" tests. This is in line with what Navid wrote. In real life, the wind conditions are continously changing, the blade is rotating and it is also not a rigid body. However, especially for conceptual design, often the inflow is considered uniform, the turbine rigid. This reduces significantly the undertainities about the design. Talking about tests, wind tunnel tests on the single airfoils or on scaled blades are stationary kind of tests.
I fully agree with Francesco! Static tests are entering the realm of structural design. As for the use of quasi-2D stationary wind tunnel measurements for the design of rotating blades operating under extreme turbulence and gusts....well that is another huge discussion :D
I believe Navid has hit closer to the appropriate answer to this question. While "static" for mechanical engineers often implies a type of structural test, to the aerospace engineer it usually implies a condition of relative motion. To be able to apply simplified HAWT analysis techniques such as blade element analysis or blade element momentum approaches, one must start with the 2D lift, drag, and pitching moment data for the wing section(s) that make up the entire blade. This data does not take into account dynamic phenomena like dynamic stall, etc.
The word "aerodynamic" means there is a relative movement between the air and the blade, which leads to the aerodynamic forces (lift, drag) on the blade. Using the word "static" together with "aerodynamic" is a bit confusing. But I think the word "static" here simply means the blades are motion-less (with fixed position and attack angle) in the test.
Hi everybody,
Patrick and Navid are close. But to be more accurate, static here means steady forces. For wind turbine blade analysis it is normal to "initially" study the static (constant) forces and their effects on the blades and the power output of the said turbine.
But When Qing asked about static testing I also am not sure!! May be it is meant to be at constant wind speed and rpm of the turbine??
I hope my answer do help.
Wan Zaidi
Do you mean static balancing of the rotor. In turbine practices rotor are statically balance and dynamically balance. The procedure for static balancing is very simple
- Badges
- Science topic
- Similar topics
- Engineering
- Thermal Engineering
- Thermofluid
- Fluid Mechanics
- Fluid Dynamics