How CFD and Engineering Assisted a Helicopter Landing on a Navy Ship.
With the correct use of CFD and aeronautical engineering, ATS participated in supporting the landing of a helicopter on the Brazilian Navy’s corvette Barroso in adverse wind conditions and rough seas.
The use of computational fluid mechanics for the analysis of the flow around the Barroso corvette was essential, as this in-depth study was needed to define the correct landing envelope of this helicopter in an unfavorable wind situation.
The ATS accepted the challenge and made excellent use of its knowledge of fluid mechanics, CFD and aeronautical engineering, detecting the difficulties of the study and proposing solutions.
The challenge: To create a relationship between the wind conditions measured by the instrumentation of the ship and the flow that affects the helicopter.
For a helicopter to land safely, the wind speed and direction at all points along the landing path must be within the landing envelope.
In the case of the Barroso corvette, the anemometer, a device that records the speed of the winds and also their direction, is located at the front of the ship. Therefore, there is a disturbance in the flow from the front of the ship to the helicopter landing site, resulting in the measured speed of the ship not being exactly the same as the landing path of the helicopter.
Therefore, ATS developed simulations of ship and helicopter conditions through CFD to calculate the correct flow, employing aeronautical engineering to solve the problem.
The solution: How engineering and computational fluid mechanics were used to develop the landing envelope.
To reach a solution on how to develop the landing envelope in these adverse conditions, simulations were created with the CFD++ software to relate the wind measured by the ship’s anemometer with the wind speed at several points along the landing path.
Thus, the characteristics of the flow at the stern of the Barroso corvette, on the helicopter landing deck and in the waiting positions for landing on its sides were determined.
To validate the results, we used results from a wind tunnel test carried out at the NLR (Netherland Aerospace Centre), where a scale model of the corvette was created and exposed to varying conditions of wind speed and direction.
During the tests, a turn table was used to obtain the rotation of the prototype ship, and it was represented in CFD through a mesh generated with the software Ennova Meshing, producing a mesh of high quality prisms over the entire geometry of the model. The mesh of 20 million elements rotated in relation to the farfield, creating a faithful representation of the wind tunnel test.
In this experiment, an anemometer was used to measure the wind, fixed to a structure above the model of the ship. However, throughout the CFD simulations, it was noticed that the structure that supported the anemometer in the Barroso corvette was compromising the flow, soon interfering with the result to design the correct landing of the helicopter.
To circumvent the problem of the interference of the anemometer’s support structure on the results, another wind tunnel test was developed at the IAE (Instituto de Aeronáutica e Espaço), in São José dos Campos, but this time, using PIV (Particle Image Velocimetry) , technique with laser and microscopic particles to measure, in a less intrusive way, the speed and direction of the wind. This new test made it possible to measure the flow velocity vector in several planes along the study region.
This entire process of comparing the data from the PIV test, from the experiments with an anemometer at the NLR, and from the results obtained through simulations with the CFD++, enabled the definition of an adequate landing envelope with high precision.
After this work carried out by ATS, the conclusions obtained were accepted by the Brazilian Navy and are being used to develop a program that will relate the wind measured by the ship with the wind that affects the helicopter, thus facilitating the landing of any other helicopter in the area. of a ship similar to the corvette and, consequently, increasing the safety in the landing process.
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