Numerical investigations of micro bubble drag reduction effect for container ships

Abstract

In the course of the most recent thirty years reduction of ship resistance and saving fuel consumption to accomplish higher speed with reduction of pollutants has been the significant subject for researchers. Micro bubble drag reduction technique is the one of the most interesting thoughts in this field owing to its great advantages, such as considerable potential drag reduction, easy operations, environmental friendliness and low costs. In this study a 3-D numerical investigation into frictional drag reduction by air micro bubbles is applied on KRISO container ship model. The objective is to understand the mechanism of resistance reduction through micro bubbles injection under model ship at different Froude numbers, injection rate and of course volume fractions. The numerical simulations are performed using a commercial CFD code solving Reynolds averaged Navier-Stokes (RANS) equations. For more than 36 simulations has performed to investigate the effect of injection of micro bubble under ship model hull and to estimate the local Coefficient of friction values along ship hull model. The results show that at all of the examined Froude number, frictional resistance reduction attained but at different rates and a maximum drag reduction of 27.6 % obtained at 0.282 Froude number with 4.8 % air volume fraction. Keywords ship resistance • KRISO ship model • container ship • micro bubble • drag reduction • numerical simulation • ANSYS FLUENT Marine systems and ocean technology j o u r n a l manuscript No.

Effect of feathers on drag in plunge‐diving birds

“…This phenomenon is thought to involve air trapped under feathers that is released to lower drag during the jump 6 . Micro‐bubbles, which attach to and are emitted from the hydrophobic feathers, 7 indicate the free‐shear boundary condition on the body, thereby reducing drag 8–14 . Additionally, plunge‐diving birds have been observed to release bubbles from the air trapped in their underlying feathers (see Figure 1A) as they descend while plunging and rapidly swimming 3 .…”

“…6 Micro-bubbles, which attach to and are emitted from the hydrophobic feathers, 7 indicate the free-shear boundary condition on the body, thereby reducing drag. [8][9][10][11][12][13][14] Additionally, plunge-diving birds have been observed to release bubbles from the air trapped in their underlying feathers (see Figure 1A) as they descend while plunging and rapidly swimming. 3 Despite some studies demonstrating a relationship between drag and the feathers of surface-diving birds, 15,16 the effect of the bubble release of plungediving birds on drag remains unexplored.…”

Directional Transport of Underwater Bubbles on Solid Substrates: Principles and Applications

“…For instance, bubbles adhering to the electrode would hinder the contact between the electrode and the electrolyte, thereby reducing the efficiency of the electrochemical reaction. − Bubbles can also adhere to underwater cameras or diving goggles, which results in poor visibility . On the other hand, attaching bubbles to the surface of the underwater vehicle can significantly reduce the resistance between water and the vehicle. − It is also found that attaching bubbles can enhance the sealing performance of biological suckers , and artificial suckers . Therefore, the reliable manipulation of bubbles on the substrate is of vital importance.…”

Bio-based synthesis of a sustainable Nano drag reducing agent for sprinkler irrigation systems

“…One of these methods relies on the use of baffles of various heights in the turbulent flow zone to suppress turbulent eddies [1]. Other methods include oily materials or bubble layers to decrease skin friction [2]. However, adding minute amount of chemical agents to fluids delivered through pipes is the most effective method of reducing drag [3].…”