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Axisymmetric Wake Neutral

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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 x1/3

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 umax2/U02 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.