Showing papers by "Manhar R. Dhanak published in 2022"
TL;DR: In this paper , the effects of limited water depth on the hydrodynamic performance of a catamaran with the full-scale dimensions and geometry of a WAM-V 16 unmanned surface vehicle operating in shallow waters are investigated using an incompressible URANS-VOF solver in OpenFOAM®.
Abstract: The effects of limited water depth on the hydrodynamic performance of a catamaran with the full-scale dimensions and geometry of a WAM-V 16 unmanned surface vehicle operating in shallow waters are investigated using an incompressible URANS-VOF solver in OpenFOAM®. Simulations of the flow associated with the passage of the catamaran in shallow waters have been conducted for a range of vehicle speed and several shallow to intermediate water depths under free trim and sinkage conditions. The effects of water depth on the resistance and the dynamic motion of the catamaran are characterized. The total resistance coefficient of the catamaran is shown to increase by as much as over 40% at transcritical Froude numbers, close to the critical depth-dependent Froude number (Frh=1.0). The wave system associated with the flow is examined and its relationship to observed impacts on resistance, trim and sinkage are discussed. The effect of limited water depth on Kelvin’s wake angle is characterized in terms of both length and depth Froude numbers and is shown to be in good agreement with theory.
3 citations
DOI•
17 Oct 2022
TL;DR: In this article , the design and fabrication of a marine hydrokinetic turbine for deployment from a floating unmanned autonomous mobile catamaran platform is described, and a prototype system is targeted at supporting development of self-powered autonomous mobile recharge stations for unmanned aerial vehicles in coastal zones.
Abstract: Design and fabrication of a marine hydrokinetic turbine for deployment from a floating unmanned autonomous mobile catamaran platform is described. The objective is to develop a low-flow current turbine for deployment from a floating mobile catamaran USV platform. An undershot water wheel has been selected as the turbine of choice and a WAM-V 16 catamaran has been selected as the USV platform. The concept of operation is that the USV platform would autonomously seek and navigate to a coastal location where coastal or tidal currents may be present, anchor at the location, and deploy the turbine to harness the current energy, convert it to electricity and store it in onboard battery banks. The prototype system being developed is targeted at supporting development of self-powered autonomous mobile recharge stations for unmanned aerial vehicles in coastal zones. Once implemented on the vehicle, open water tests are planned for a range of environmental conditions, involving tidal and coastal currents, and system configurations. The status of the ongoing effort will be discussed.
DOI•
17 Oct 2022
TL;DR: In this paper , a study of the proper placement of a total field QuSpin magnetometer on a REMUS 100 AUV and required denoising for sufficient isolation of the sensor from magnetic self-noise of the AUV is presented.
Abstract: A study of the proper placement of a total field QuSpin magnetometer on a REMUS 100 AUV and required denoising for sufficient isolation of the sensor from magnetic self-noise of the AUV is presented. This study is in support of a long-term goal to aid geophysical navigation based on sensing of the total magnetic field and bathymetry. Field tests were conducted in an isolated marine environment with the magnetometer placed on a pole at various distances ahead of the nose of the AUV. First, ambient magnetic field was measured over periods of several hours at various times of the year, to determine the range of variability of the field under natural conditions. Then the impacts of the internal and external sources of magnetic self-noise on the measured field were examined. Low-pass wavelet filtering was used to digitally reduce the fluctuations caused by sources of internal and external magnetic interferences, including energized onboard electronics and the AUV’s DC motor used for its propulsion, as well as skin depth and coastline effects. Vehicle motion-induced interferences, such as induced magnetic field and eddy currents, were also examined, to determine whether a Tolles-Lawson model-based motion compensation would be necessary. A two-stage measurement and analysis procedure was developed. Placing the total field magnetometer at a minimum distance of 0.4m ahead of the vehicle’s nose appears to provide sufficient isolation if wavelet lowpass filtering is applied with a cutoff frequency of 0.1 mHz. However, significant improvement is obtained if the magnetometer is placed 0.9 m ahead of the vehicle’s nose.
DOI•
17 Oct 2022
TL;DR: In this article , the hydrodynamic performance of a catamaran with full-scale geometry of a WAM-V 16 unmanned surface vehicle operating in limited-depth waters is investigated.
Abstract: The hydrodynamic performance of a catamaran with full-scale geometry of a WAM-V 16 unmanned surface vehicle operating in limited-depth waters is investigated. Resistance, sinkage and trim of the catamaran in shallow to intermediate water depths are characterized over a range of Froude numbers using unsteady Reynolds-averaged Navier-Stokes modeling and simulation of the catamaran’s motion under free trim and sinkage conditions. Wake characteristics, including wave patterns in the wake and Kelvin wake angle, are described. The performance of the catamaran’s motion in head and following seas in waves transforming over a beach is described.