The experimental result of measurement of axial hydrodynamic forces on a yawed smooth circular cylinder in a uniform stream is presented. The result will be very useful for estimating the behavior of a thin cable towed at various yaw angles and subjected to ambient currents. The measurements were conducted for small and intermediate Reynolds numbers where accurate experimental results are lacking. The key to the success of this experimental investigation is the design and construction of a force measurement system based on the principle of analytical balance. The axial drag coefficient, % is found to be dependent on the Reynolds number as well as yaw angle. Comparisons with existing theoretical results at moderate and low Reynolds numbers are made.
Study of axial hydrodynamic force on a yawed cylinder or cable has been the topic of numerous investigations in the past 80 years. The earliest study that we could find is a report by Relf and Powell (1917), Choo and Casarella (1971) has made a comprehensive literature review on hydrodynamic resistance of towed cables up to that time. However, It has occurred to us that accurate and reliable measurements for small and intermediate Reynolds numbers on this subject are still lacking at the present time. Since yawed cylinders or cables have wide practical oceanographic applications, such a basic information is deemed essential for reliable prediction of deployment of cables. Measurements of axial hydrodynamic force on a yawed smooth cylinder in a uniform stream were carried out in our laboratory. The experimental results have been compared with theoretical results of Chiu and Lienhard (1967) for intermediate Reynolds numbers and with that of Tomotika et al. (1953) for low Reynolds numbers. The comparison was found to be very good, thus assuring the accuracy and reliability of this measurement result.
