# Axisymmetric Wake Neutral

**Scope**

The benchmark is open to participants of the Wakebench project using flow models to calculate wind turbine wakes. Completion of the benchmark will demonstrate that a simulation approach is capable of capturing the physics necessary to predict behavior of an isolated wake.

**Objectives**

Evaluate models using a theoretical solution to assure that they can capture an important component of wind turbine wake flows.

**Data Accessibility**

The benchmark is offered to participants of the IEA Task 31 Wakebench. In the future it will be open for public access

**Input data**

The wake profiles being compared should meet the following criteria required for equilibrium similarity:

*x/θ*> 100, and*U0δ*/ν*> 500

**Validation data**

The validation exercises to be performed consist of the following comparisons.

- Demonstrate the wake width grows as
*x*1/3

Note that *a* is an adjustable parameter that depends on a particular simulation boundary conditions

- Demonstrate that the wake deficit velocity decays as
*x*-2/3,

Note that *b* is an adjustable parameter that depends on a particular simulation boundary conditions.

In addition to these fundamental comparisons, the model results may also be used to demonstrate other properties of equilibrium similarity.

- The wake velocity deficit profiles and axial normal Reynolds stress profiles collapse when suitably normalized. For the wake deficit, plot

and, for the Reynolds stress, plot

- Alternatively, demonstrate that
*umax*2/*U0*2 is constant.

**Model runs**

The modeler is left to developing the means of simulating a wake. Starting the solution with a wake profile to begin with and allowing it enough time to evolve downstream before assessing results is one possible approach.

**Output data**

Provide plots of the processed simulation results compared to the theoretical results provided above.

**Remarks**

There are no guidelines on the definition of the computational mesh so please describe how you integrate grid dependency in the evaluation process.

**Terms andConditions**

Not applicable.