# NREL Phase IV wind turbine The NREL Phase IV wind turbine has two blades with NREL S809 airfoil featuring non-linear twist and linear taper. The turbine radius is $$R=5.029$$m and the aspect ratio is $$AR=6$$. This case considers the turbine with a collective pitch of $$\theta=5$$deg, rotating at $$\omega=71.9$$rpm, at a freestream velocity of $$|\mathbf{V}\_{ref}|=7$$m/s. A structured mesh with 15 elements in the chordwise and 32 elements in the spanwise direction (for each blade) is used. The results are obtained with an azimuthal step of $$\Delta\theta=6$$deg ($$\Delta t=0.0139$$s) for 3 revolutions. The image below shows the pressure coefficient distribution. ![](/files/-Mh5F8jU-Pxe6Sf-WBcj) The animation below shows the development of the wake. {% embed url="" %} NREL Phase IV wind turbine wake development {% endembed %} The images below show the pressure coefficient at $$r/R=0.47$$. The experimental results from Hand et al. \[1] are shown for comparison. ## Files {% file src="/files/-MgbQkB6x5Op\_Ml9Elai" %} ## References \[1] Hand, M. and Simms, D., “Unsteady aerodynamic experiment phase VI: wind tunnel test configurations and available data campaigns,” NREL Technical Report TP-500-29955, 2001 --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.aviumtechnologies.com/nrel-phase-iv-wind-turbine.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.