International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 12 Issue: 01 | Jan 2025
p-ISSN: 2395-0072
www.irjet.net
Measurement of drag coefficients of underwater vehicles using the power consumption method Jaeho Chung1 1Yonam Institute of Technology, Professor, Dept. of Mechanical Engineering, Jinju, Republic of Korea
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Abstract - The most widely used method of measuring the
Cho’s study [4], which studied the underwater supercavitation phenomenon, and this paper presents a more specific methodology for the power consumption method.
drag of an underwater object is to attach a sensor directly to the object. In addition, the classic method of measuring drag by attaching a rope or string to an underwater object is also used. However, these methods are known to be accurate in measuring the drag of a moving body at sea level in the form of a general ship, but they are not used in measuring the drag of a moving body in the deep sea where water pressure acts or an underwater moving body where a supercavitation phenomenon occurs. For that reason, this study conducted to develop a drag measurement method for underwater vehicles that is not subject to these limitations. In this study, we measure the power used by an underwater vehicle and measure the drag of the underwater vehicle from the power.
2. Experimental set-up
Key Words: Drag coefficient, Drag force, Power consumption method, Underwater vehicle, Supercavitating vehicle
Fig -1: Experimental setup
1.INTRODUCTION
To measure the drag coefficient of an underwater vehicle, an experiment was conducted using a tank designed as shown in Figure 1. The tank size is 19.2 m in length, 1 m in width, and 1 m in height, and the side walls of the tank are made of transparent glass for external observation. The towing system is a combination of a modified batterypowered remote-controlled (RC) car and two straight rails laid along the entire length of the tank. The RC car runs along the rails at a maximum speed of 10 m/s, and the RC car and the underwater body are rigidly attached to each other via a right-angled C-shaped connecting bar. Therefore, the underwater vehicle moves with the camera at the same speed as the RC car.
Several studies have been conducted to study the hydrodynamic forces, especially drag, acting on moving underwater bodies. These trends demonstrate the importance of developing drag prediction method. Additionally, these drag measurement studies were conducted in conjunction with drag reduction methods [16]. Over the past two decades, various methods have been proposed to measure the drag coefficient of moving underwater objects. Yao et al. [7] and Jourdan et al. [8] proposed a method of measuring the drag coefficient of an underwater moving object in a specific Reynolds number range using a speed sensor and a pressure sensor in a water tunnel. Venukumar et al. [9] proposed a method to measure the drag coefficient of an object in a supersonic flow using an acceleration sensor, a speed sensor, and a pressure sensor. Sridhar and Katz [10] used the PIV system to find acceleration and velocity and devised a method to measure the drag coefficient of an object. In addition to these studies, various methodologies were proposed to measure the drag coefficient of underwater vehicles, but most used speed sensors and pressure sensors. Accordingly, this study presents a method to measure the drag coefficient of an underwater vehicle using power consumption. The power consumption method proposed in this study was used in Chung and
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In this study, the drag force (FD) of the underwater vehicle is obtained from the power consumption of the battery consumed when the RC car is running. As shown in Figure 2, the power consumption was measured using a voltage sensor and a current sensor. FD P / V
(1)
P Voltage Current
(2)
In the equation (1) above, P represents the power consumption and V represents the speed of the underwater vehicle.
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