Trans RINA, Vol 161, Part A4, Intl J Maritime Eng, Oct-Dec 2019
speed and have recorded changes in the air flow structure on the helodeck.
2.3 (h) Effect of Ship's Exhaust
Kulkarni et al (2005a) have undertaken a detailed review of the smoke nuisance problem on ships. The authors have brought out that the performance of gas turbines of fixed and rotary aircrafts are very sensitive to ambient conditions. The risk of compressor stalling increases significantly with a momentary temperature rise of 3⁰ C or more. The 3⁰C isotherm should therefore be at least 15m higher than the helodeck. For ships where the exhaust is directed in such a way as to impinge on the landing/ take- off path of the helicopter, the effects of ship's exhaust gases need to be considered on Pilot Workload. The data from wind tunnel studies undertaken by Kulkarni et al. (2005b) provided the physical quantities that could directly be correlated to the results of the numerical simulations. The authors have also presented the results of a detailed parametric investigation using CFD for a total of 112 different cases for exhaust smoke interaction with the superstructure by studying four velocity ratios (K=1, 2, 3 and 4) (the ratio of exhaust velocity to the ambient wind over deck relative velocity), seven yaw angles () (0⁰ to 30⁰ in steps of 5⁰) and four superstructure configurations (Kulkarni, 2007).
Vijayakumar et al (2008) have undertaken extensive studies on superstructure configuration of Naval ships towards optimising the funnel heights in order to avoid smoke nuisance on the ship superstructure. The authors have carried out CFD simulations for different funnel heights to mast height ratio ranging from 0.35 to 1 along with Gas Turbine intakes for wind directions (yaw angles) between -30⁰ to 30⁰ at interval of 5⁰ and for three velocity ratios (K=0.5,1 and 1.5). The emphasis of the study was to provide guiding polar plots for the designer to choose the appropriate funnel height for the naval ships during the earliest stages of design. Vijayakumar et al (2014) have presented the comparison of CFD simulations with the published results for two cases, namely hot jet in a cross flow and hot exhaust with a cross flow on a generic frigate. Vijayakumar et al (2012) have presented the results of flow visualization studies undertaken in a wind tunnel over a simplified superstructure of a generic naval ship in order to understand the effect of various parameters like mast size and location, gas turbine intakes, and funnel-to-mast height ratios on the exhaust plume path. These investigations have been carried out at four velocity ratios for three configurations of simplified superstructure. The result of these flow visualization studies provides insight into the process of plume dispersion in the vicinity of the funnel and other structures on the topside of naval ships. Landsberg
et.al (1996 & 1995) report carrying out 3-D unsteady smoke and temperature time history computations in the helicopter landing zone and the ingestion of smoke into the helicopter hangars. Landsberg and Sandberg
(Camelli, et al, 2004, Landsberg, et al, 1996 and Landsberg, et al, 1993) report the use of the CFD code FAST3D to compute the unsteady air wake about the LHD aircraft carrier and compute the temperature profile of the hot exhaust plume from the DDG–51 destroyer for the US Navy.
2.4
INTEGRATION OF SIMULATION RESULTS WITH PILOTED FLIGHT SIMULATIONS TO QUANTIFY SHOL
On the lines similar to Offshore Industry, in recent times, few countries have channelled their efforts towards modelling and simulation of the ship–helicopter dynamic interface to augment the SHOL definition process (Forrest et al, 2012). A great deal of this effort has focused on improving the fidelity of piloted flight simulators such that the results from simulated SHOL trials are comparable to those from at-sea flight trials. Forrest et al (2012) bring out the potential benefits offered by the dynamic interface simulation, including the following:-
(a) Identification of Wind over Deck (WOD) “hot spots” before at-sea testing which can be used to inform the flight-test program.
(b) The ability to assess particular WOD conditions which may have been missed during at-sea testing in order to maximize the operational envelope.
(c) Investigation of flight deck aerodynamics while new ships are still at the design stage to identify potential improvements to superstructure design, landing spot locations and placement of equipment.
(d) A greater understanding of ship air-wake turbulence and the mechanisms which cause it.
(e) A realistic simulation environment in which to conduct pilot training exercises.
As part of a review of collaborative Dynamic Interface (DI) modelling activities under the auspices of TTCP, Wilkinson et al. (1999) has described the development of a ship–helicopter simulation facility based at the United Kingdom’s Defence Evaluation and Research Agency. The simulated air-wake module is based on the superposition of basic flow patterns, with turbulent fluctuations provided by scaled random velocity time histories. Because of the empirical nature of this air-wake database, the three-dimensional components of turbulence are not correlated.
In a study conducted by Lee et al. (2003), a dynamic interface simulation of the UH-60A helicopter operating off an LHA ship was developed with an objective of understanding the impact of a time-varying ship air-wake on the pilot control activity for an approach operation, and to develop a human pilot model for analyzing the pilot workload.
Forrest et al (2012) have presented the results for a series of piloted flight simulation trials in which an SH-60B Sea
A-412
©2019: The Royal Institution of Naval Architects
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166
