A spectral analysis of laser Doppler anemometry turbulent flow measurements in a ship air wake

Abstract

Helicopters are one of the most important tactical elements in maritime operations. The necessity to improve the conditions in which the landing and takeoff operations are carried out leads to the study of the flow that separates from the ship's superstructure over the flight deck. To investigate this flow a series of wind tunnel experiments have been performed by testing a sub-scale model of a frigate. Measurements of the flow velocity have been taken by means of laser Doppler anemometry in five points that simulate the last path of the landing trajectory. The data obtained in these experiments is analyzed in the frequency domain where the corresponding spectra are calculated. Onboard measurements from an actual full-scale frigate are analyzed and compared with the wind tunnel results. Conclusions obtained consist of a series of illustrative values of turbulent energy frequency ranges, which are valuable for any study in this field. The comparison shows a similarity between both experiments, reasserting the role of the wind tunnel measurements in these kind of studies.

Aerodynamic effect of the aircraft carrier island on flight deck flow with cross wind

“…An in-house MATLAB code 30 has been used to compute the power spectral density (PSD) which shows the distribution of the turbulent energy in the air wake.…”

“…An in-house MATLAB code 30 has been used to compute the power spectral density (PSD) which shows the distribution of the turbulent energy in the air wake. All the measurements have been obtained at spot 4 (Figure 2) of the aircraft carrier model providing the PSD.…”

Experimental Investigation of the Aerodynamic Flow in the Aircraft Carrier Ski-jump by means of PIV

“…Flow field configuration is affected by wind direction, ship motion and aircraft operational attitude [1,2]. Regarding that helicopter operations can be performed at different conditions [8], the flow encountered by the helicopter near or over the flight deck is highly complex and unsteady [9,10]. Crosswind direction is the critical one due to the fact that the massive flow detachment generates a turbulent shear layer and a low velocity recirculation bubble over the flight deck [1,2,11].…”

An Inertial Sensor to Measure Wind Turbulence With RC Helicopters

“…During testing, scaled down model of test bodies (vessels) are made to interact with controlled streamlined wind flow (to match Reynold's number) and the resulting turbulent wind pattern is measured. Such wind tunnel setups utilize a variety of anemometric modalities including laser sensing [4], hot wire anemometers [2,5] and Particle Image Velocimetry [6,7]. Although the transducers used in the wind tunnels are extremely sensitive, due to very high cost they cannot be deployed outside the limited test area of a wind tunnel.…”

“…Use of outdoor anemometers is another common means for in-situ wind pattern measurement. Multiple ultrasonic anemometers are placed at different locations on the flight deck of the naval vessels and the measurements are compared with CFD/Wind Tunnel testing results [2,4,8,9]. In this methodology, the high cost of the anemometers limits the number of anemometers used simultaneously, whereas moving the sensors to different positions is time consuming.…”