Sustainable Marine Structures

Flow Structures around a Sphere Attached to the Bottom of a Prismatic Sloshing Tank: Problem‑Oriented Basic Research

Murat Aksel

Department of Civil Engineering, Alanya Alaaddin Keykubat University, Alanya 07425, Antalya, Türkiye

Oral Yagci

Civil Engineering Department, Engineering Faculty, Aydin Adnan Menderes University, Aydin 09010, Türkiye

Manousos Valyrakis

Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki 54645, Greece

Veysel Sadan Ozgur Kirca

Civil Engineering Department, Istanbul Technical University, Istanbul 34555, Türkiye

DOI: https://doi.org/10.36956/sms.v6i2.1204

Received: 8 July 2024 | Revised: 9 August 2024 | Accepted: 15 September 2024 | Published Online: 22 September 2024

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Abstract

This study aimed to investigate the spatiotemporal variation of hydrodynamic variables around a sphere rigidly fixed to the bottom of a sloshing tank. The experimental measurement of the variations of dynamic variables around a body in a sloshing tank requires non-intrusive measurements that are usually expensive and sometimes inapplicable. Therefore, the numerical model could serve as a cost-effective tool for such problems. A two-stage analysis was conducted. In the first stage, an experimental study was carried out in a testing system comprising a water tank with uniaxial freedom of movement constructed on a monorail operated by a computer-controlled step motor. The primary objective of the experiments was to generate reliable data for calibrating the numerical model.

During the experiments, the tank's movements were recorded using an accelerometer and ultrasonic sensors with a sampling frequency of 200 Hz for each. The accelerometer and ultrasonic sensor data were used to impose the motion of the sloshing tank into a Reynolds-Averaged Navier-Stokes (RANS)-based numerical model. The video recordings, which comprised temporal fluctuations of the water surface, were used to calibrate the Model 1. Once the first numerical model was calibrated based on water surface level records using image processing methods, the second numerical model was constructed to accommodate a rigid spherical body with a 17 mm diameter connected to the bottom of the sloshing tank. The initial and boundary conditions used in the second numerical model were identical to those used in the first model to measure the spatiotemporal fluctuations of the surrounding spherical body's kinematic and dynamic variables, respectively. The findings revealed that sloshing motion exerts a significant impact on the boundary layer separation process around the sphere. It was also witnessed that the stage of the sloshing motion controls the temporal lag between the pressure, velocity and water surface level.

Keywords: Boundary Layer Separation; Drag Force; Particle Hydrodynamics; Sediment Transport; Sloshing Tank; Oscillatory Flow; Wake Region

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