Hydrodynamic Performance Analysis Research Articles

Analysis of hydrodynamic performance and acoustic characteristics of loop propellers

To improve the efficiency and stealthiness of marine operations of autonomous underwater vehicles (AUVs), 12 loop propellers with different structural parameters are selected as research subjects. The Reynolds-averaged Navier–Stokes equations method is used to simulate the flow field result around the loop propellers and is combined with detached eddy simulation and the acoustic analogy method for hydrodynamic analysis and noise prediction. The influence of three structural parameters, namely the number of propeller blades, the thickness of propeller blades, and the pitch of propeller blades, on the hydrodynamic and noise performance of the propeller is investigated, and the loop propeller structure with the optimal hydrodynamic and noise performance is selected. The research results indicate that increasing the number of propeller blades and increasing the pitch of the loop propeller can significantly improve the thrust and torque of the propeller and effectively reduce the noise. However, increasing the thickness of the propeller blades can also increase the thrust and torque of the propeller, but it will sacrifice the noise performance of the loop propeller to a certain extent. The sensitivity of the noise performance with respect to the blade thickness is significantly higher than that of the two parameters of blade number and pitch. To verify the accuracy of the hydrodynamic and noise performance simulation results, this study conducted hydrodynamic and noise performance tests on the preferred loop propeller structure in the towing pool and anechoic pool and successfully verifies the reliability of the numerical simulation method used in this study for the prediction of the propeller performance by comparing the test data with the simulation results. This study provides theoretical support for the design optimization of loop propellers and helps to promote the design of high-efficiency and low-noise propellers in complex marine environments.

Research on layout optimization for propellers of a submarine operation vehicle

The submarine operation vehicle was an important equipment for exploring the marine environment and performing underwater tasks. In this paper, the calculation and analysis of hydrodynamic performance and the layout optimization of the propellers under different layouts were completed. Based on the left-right symmetrical layout of the four ducted propellers, the two ducted propellers were taken as the research object to optimize its vector layout, and an approximate model was constructed according to the numerical calculation results under different combinations of propeller spacing and deflection angle. The simulation calculation and verification are carried out, and the optimal layout of the four ducted propeller were determined considering the interference between the ducted propellers on both sides. Finally, an experimental platform for the thrust test of the two ducted propellers were built. It was found that the axial thrust ratio of the rear propeller and the front propeller in experimental results were in good agreement with the simulation results, which verified the feasibility of using the numerical simulation method to study the mutual interference between the ducted propellers.

Ship hydrodynamic performance analysis and model construction based on CFD method

Abstract CFD method has the advantages of high forecast accuracy, wide applicability, strong stability of calculation results, and low cost, and nowadays it has been widely used in various fields. The CFD method has many advantages when applied to ship hydrodynamic performance analysis, specifically to ship hydrodynamic performance prediction, problem mechanism research, and performance optimization. Based on this, this paper utilizes the CFD method to carry out a model analysis of ship hydrodynamic performance. By analyzing the propeller efficiency, the reasoning force and torque of the double propeller in the symmetric case are decreased. However, the efficiency is improved by 1.4% compared with the asymmetric case, which shows that the method adopted in this paper can effectively improve the ship hydrodynamic force. Through the above research, we aim to provide a certain reference for the improvement of ship hydrodynamic performance.

Hydrodynamic performance analysis of dual vertical axis turbine

Abstract This article adopts a biomimetic approach and uses the profile of the fastest sailfish in the ocean as the airfoil profile of a water turbine. Integrating centrifugal and axial flow turbines on one drive shaft can effectively integrate wave and current energy (wave current integration). The wake of a centrifugal turbine flows into the flow field of an axial flow turbine, and based on the Kantar effect, the energy harvesting coefficient of the axial flow turbine is improved. The five blades of the axial flow turbine and centrifugal turbine are subjected to uneven forces, resulting in torsional and radial forces on the drive shaft, causing periodic series motion of the turbine and reducing the overall lifespan of the machine.

Hydrodynamic performance analysis and diving trajectory prediction of a novel deep-sea lander with flapping hydrofoils

Traditional deep-sea landers lack maneuverability during the diving process, making it difficult to effectively regulate the diving trajectory and velocity. In this paper, a novel deep-sea lander with flapping hydrofoils is proposed, and the simplified geometric model and typical flapping modes are introduced. Through computational fluid dynamics (CFD) simulation, the effectiveness of the flapping hydrofoils in regulating the diving trajectory and velocity of the lander is verified, and the influence of the amplitude of flapping angle and flapping frequency of the hydrofoils on the maneuverability of the lander and the propulsion efficiency and deceleration ratio of the flapping hydrofoil is explored. The relationship between the thrust generated by flapping hydrofoils and the maneuverability of the lander, as well as the relationship between the vortex topology and the propulsion efficiency and deceleration ratio of the hydrofoil are explained, respectively. And the diving trajectory of the lander is predicted based on Gaussian process (GP). The results show that the lander can have a certain degree of maneuverability through flapping hydrofoils, and the prediction error of the diving trajectory is within 4%. This paper provides reference for the design and application of the novel deep-sea lander with flapping hydrofoils.

Analysis of hydrodynamic performance of underwater accompanying robot based on CFD

Analysis of hydrodynamic performance of underwater accompanying robot based on CFD

Hydrodynamic performance analysis of swimming processes in self-propelled manta rays

To fill the research gap regarding the whole process (steady-state and nonsteady-state phases) of median and/or paired fin (MPF) mode swimming in underwater organisms, a two-degree-of-freedom self-propelled coupling method of motion and hydrodynamics based on user-defined functions of Fluent software was established, and numerical simulations were carried out for the startup, acceleration, and steady-state phases of manta rays. The interaction mechanism among the hydrodynamic characteristics, vortex evolution, and pressure distribution was investigated in the mentioned phases. We concluded that the negative pressure zone generated by the leading edge vortex and the shear layer contributes to thrust generation and changes in swimming velocity dominate the hydrodynamic characteristics by affecting the evolution of the shear layer and the leading edge vortex, with a 17.54% increase in forward average velocity in the fourth cycle compared to the third cycle and a consequent 9.5% increase in average thrust. In the end, the relationship between the formation of trailing edge vortex rings and changes in thrust was revealed. The vortex ring contributes to the increase in thrust, but the formation of the vortex ring comes at the cost of the loss of the leading edge vortex negative pressure zone, which greatly affects thrust, decreasing to 38.3% of its peak. The swimming mechanism revealed in this study provides a reference for the study of MPF-driven biodynamics and a new simulation strategy for the prediction of bionic navigator motions.

Hydrodynamic performance analysis of formations of dual three-dimensional undulating fins

The work seeks to understand the hydrodynamic performance and interaction mechanisms of double-fin formations. A high-resolution numerical technique based on the constraint immersed boundary method is used for simulating the 3D double-fin system. Comprehensive analysis is carried out, focusing on the hydrodynamic performance of formations with various arrangements, phase differences, and spatial distances. The result shows that the side-by-side formation can suppress the thrust of the fins while reducing energy consumption. The tandem formation notably enhances the thrust for the fin positioned at the rear, albeit at the cost of increased energy consumption. In the tandem formation with a small spacing, the following fin can obtain a thrust increase of 28% and an efficiency increase of 10%, independent of the phase difference. The thrust enhancement in the tandem formation is related to the suction-based propulsion mechanism induced by hydrodynamic interactions. However, the interaction mechanism between the two side-by-side fins resembles the so-called channelling effect. The unilateral channel flow perturbs the pressure equilibrium on either side of the fin, potentially imposing additional resistance on the undulating fin, with effects depending on the phase difference. The study offers new insights into understanding the collective behaviours of undulating fins.

Evolution mechanism and parametric investigation of relative negative pressure zone in spiral groove gas face seal for aero-engine at high rotational speed

As an advanced sealing technology, spiral groove gas face seal has excellent sealing performance. However, it is rarely used in aero-engine. Previous investigation proposed that the relative negative pressure zone (RNPZ) in the spiral groove gas face seal can regulate the sealing performance. In this paper, further numerical simulation work is carried out. By quantifying the obstruction effect, viscous pumping effect and shear effect, the evolution mechanism of RNPZ under different film thicknesses and groove depths is revealed. Then, the parametric analysis of spiral groove configuration and groove number is carried out. Through the sub-regional quantitative analysis of the groove, the influence mechanism of structural configuration on RNPZ is revealed. Finally, combined with the hydrodynamic performance analysis, the spiral groove seal structure under optimal conditions is obtained. It is found that under the condition of high speed and low inlet pressure of aero-engine, RNPZ is suppressed by adjusting the structure of the spiral groove to enhance the shear effect, the pumping effect at the top of the groove and reduce the pumping effect at the bottom of the groove. When the number of grooves is 20 and the groove depth is 3 μm, the stiffness-leakage ratio of structure B and C can be increased by 10.15 % and 12.68 %, and the sealing performance is the strongest. This work can provide a theoretical and data basis for the subsequent optimization design of aero-engine gas face seals.

Design Process and Advanced Manufacturing of an Aquatic Surface Vehicle Hull for the Integration of a Hydrogen Power Plant Propulsion System

This article presents the design and manufacturing of a hydrogen-powered unmanned aquatic surface vehicle (USV) hull. The design process comprised three stages: (1) defining the requirements for a preliminary geometry, (2) verifying the hydrodynamic hull performance using computational fluid dynamics (CFD) simulations, and (3) experimentally validating the hydrodynamic hull performance and CFD analysis results through experimental fluid dynamics in a calm water towing tank. The manufacturing process utilized additive manufacturing technologies, such as fused granular fabrication and selective laser sintering, to produce the hull and other components, including the propeller and the rudder; thermoplastic materials with carbon fiber reinforcement were employed. The experimental results demonstrate that the optimized trimaran hull exhibited low hydrodynamic resistance (7.5 N), high stability, and a smooth flow around the hull (up to 2 m/s). The design and manufacturing of the USV hull met expectations from both hydrodynamic and structural perspectives, and future work was outlined to integrate a power plant, navigation system, and scientific equipment.

Hydrodynamic performance verification and analysis of flexible floating breakwater

Hydrodynamic performance verification and analysis of flexible floating breakwater

Hydrodynamic Performance Analysis of Wave Propelled Glider for Different Hydrofoils using CFD tools

Hydrodynamic Performance Analysis of Wave Propelled Glider for Different Hydrofoils using CFD tools

Hydrodynamic and thermal performance analysis of an inclined anchor impeller designed for yield stress food mixing applications

Mechanical agitation and mixing operations are basic processes in many industrial activities, especially in food industry. Agitation of food products with a non-Newtonian yield stress fluid and/or with a high viscosity is a common operation where standard anchor impellers are usually implemented to scrape the lateral surface of the tank. The flow generated by this type of impellers is predominantly tangential, particularly with the presence of Bingham fluids. In this regard, the present research gives a numerical investigation of the laminar flow and heat transfer of a Bingham fluid in a mechanically agitated tank equipped with an inclined anchors configuration, including the standard case. This configuration is intended for the enhancement of the axial flows specifically in the lower part of tanks, while keeping the main operation of scraping. Moreover, for heating process, the agitated system is equipped with a lateral jacket system where the temperature remains constant over time. The effects of the Bingham and Richardson numbers as well as of the anchor inclination angle are analyzed on the hydrodynamic and thermal stats. The differential balances that govern the studied phenomenon including continuity, momentum and energy equations are solved by the use of Galerkin finite element method. The results demonstrate the hydrodynamic, energetic, and thermal benefits of agitating yield stress fluids using an inclined base anchor. Indeed, significant axial hydrodynamic generation is observed with a reduced energy consumption of approximately 30% compared to the standard anchor, particularly at moderate rotational speeds. Furthermore, it enhances thermal insulation inside the mixing system and hence promoting heating process, especially in the presence of Bingham fluid and buoyancy force.

Comparative Analysis of Hydrodynamic Performance of Small Wave Buoys

The hydrodynamic performance of the floating body in seawater is very important. The wave buoy is a small buoy that measures wave parameters such as wave height and wave direction, for the non-powered wave buoy, the hydrodynamic performance mainly refers to the seaworthiness of the buoy body. Seakeeping refers to the motion law of the floating body in the wave. For the wave buoy, the seakeeping of the floating body has an important impact on the measurement of wave data. Therefore, the analysis of the hydrodynamic performance of the wave measurement float is an important reference for evaluating the performance of the wave buoy. In this paper, the hydrodynamic performance of cylindrical and spherical wave-finding buoys is compared and analyzed, and the influence of different structural forms on their hydrodynamic performance is analyzed, which provides a reference for optimizing the hydrodynamic performance of wave-measuring buoys.

Effect of combined water-jet inlets on the hydrodynamic performances in square arc-corner aquaculture tanks

To enhance the energy utilization and waste collection efficiency in a recirculating aquaculture system (RAS), this study investigates the hydrodynamic performance of a square arc-corner aquaculture tank using various combined water-jet inlets. An experimental verification system was developed for the recirculating aquaculture tank (RAT) to validate the accuracy of the computational fluid dynamics (CFD) model. This was achieved by comparing flow velocities at various monitoring points. A comprehensive analysis of the tank's hydrodynamic performance was conducted, encompassing velocity distribution, vorticity strength, flow uniformity index, resistance coefficient, Froude number, energy utilization efficiency, and particle removal rate. The results clearly showed that incorporating combined water-jet inlets greatly improved the hydrodynamic performance of the tank compared to traditional one-way inflow patterns. The combined injection method ensured a more uniform flow velocity both longitudinally and radially throughout the RAT, effectively reducing the concentration of water flow in a single direction. Additionally, the tangential injection of water flow along the tank wall promoted a more even flow rate, enhancing water mixing and maintaining a homogeneous distribution of dissolved oxygen. By arranging and spacing the injection holes appropriately, the fluidity and mixing of water were enhanced, leading to increased energy utilization and improved efficiency in pollutant collection.

Evolution and Action Mechanism of Relative Negative Pressure Zone in Spiral Groove Gas Face Seal for Aero-Engine

Abstract As an advanced sealing technology, the application of gas face seal in aero-engine is few; if possible, lower specific fuel consumption, higher thrust-weight ratio, and effective secondary flow control at minimal cost would be brought. A relative negative pressure zone (RNPZ) was found in the spiral groove gas face seal, and the evolution and action mechanism of RNPZ was investigated in detail, which may promote the above application. Three film thicknesses of spiral groove gas face seals at different rotational speeds and inlet pressures were numerically compared to obtain the pressure field in the groove area and the formation of RNPZ. Then, the radial and circumferential velocities in the groove were calculated to quantify the impact of the obstruction effect, viscous pumping, and shear effect, which revealed the evolution mechanism of the RNPZ stage by stage. At last, the action mechanism of RNPZ was clarified through the hydrodynamic performance analysis. It is found that the pressure field evolution in the gas face seal is in stage Ⅲ under the high rotational speed and low inlet pressure conditions in an aero-engine. Under the same film thickness, RNPZ can suppress leakage to a certain extent in stage Ⅱ, while in stage Ⅲ, it increases the opening force and stiffness-leakage ratio. This work can provide theory and data to help with the subsequent optimization design of gas face seals for aero-engine.

Hydrodynamic performance analysis of undulating fin propulsion

A desire to further comprehend the hydrodynamic characteristics of three-dimensional undulating fin propulsion is what motivates the work. First, a high-resolution numerical technique based on the constraint immersed boundary method is utilized to simulate the fluid-fin system. The simulation results reveal fundamental variation laws between the hydrodynamic performance of the undulating fin and kinematic parameters. According to the simulation data, an in-depth analysis of the scaling law is conducted. A key contribution of this work is to build the force scaling formula and extend the law to complicated cases involving different incoming flow velocities. The important application of the force scaling law is that it can be used to estimate the self-propelled speed and wave efficiency of the undulating fin in different kinematic conditions. The results show that the wave efficiency exhibits a monotonically bounded increasing trend as the amplitude grows, is basically independent of the frequency, and decreases monotonically with the increasing wavelength. Finally, the work discusses the evolution of vortex structures in undulating fin propulsion. The analysis indicates that the streamwise central jet formed throughout the fin body is the primary reason for thrust generation in undulating fin propulsion. Furthermore, the basic dynamic mechanisms of two types of vortex rings, related to the formation of the central jet, are investigated in the work. The results further reveal the macro-interaction mechanism between the undulating fin and fluid flow. The findings could make a contribution to explaining some biological phenomena and developing bionic engineering.

Analysis of hydrodynamic filtration performance in a cross-step filter for drip irrigation based on the CFD‒DEM coupling method

Analysis of hydrodynamic filtration performance in a cross-step filter for drip irrigation based on the CFD‒DEM coupling method

Thermal and Hydrodynamic Performance Analysis of a Shell and Tube Heat Exchanger Using the AHP Multicriteria Method

Thermal and Hydrodynamic Performance Analysis of a Shell and Tube Heat Exchanger Using the AHP Multicriteria Method

Body condition changes at sea: Onboard calculation and telemetry of body density in diving animals

Abstract The ability of marine mammals to accumulate sufficient lipid energy reserves is vital for mammals' survival and successful reproduction. However, long‐term monitoring of at‐sea changes in body condition, specifically lipid stores, has only been possible in elephant seals performing prolonged drift dives (low‐density lipids alter the rates of depth change while drifting). This approach has limited applicability to other species. Using hydrodynamic performance analysis during transit glides, we developed and validated a novel satellite‐linked data logger that calculates real‐time changes in body density (∝lipid stores). As gliding is ubiquitous amongst divers, the system can assess body condition in a broad array of diving animals. The tag processes high sampling rate depth and three‐axis acceleration data to identify 5 s high pitch angle glide segments at depths >100 m. Body density is estimated for each glide using gliding speed and pitch to quantify drag versus buoyancy forces acting on the gliding animal. We used tag data from 24 elephant seals (Mirounga spp.) to validate the onboard calculation of body density relative to drift rate. The new tags relayed body density estimates over 200 days and documented lipid store accumulation during migration with good correspondence between changes in body density and drift rate. Our study provided updated drag coefficient values for gliding (Cd,f = 0.03) and drifting (Cd,s = 0.12) elephant seals, both substantially lower than previous estimates. We also demonstrated post‐hoc estimation of the gliding drag coefficient and body density using transmitted data, which is especially useful when drag parameters cannot be estimated with sufficient accuracy before tag deployment. Our method has the potential to advance the field of marine biology by switching the research paradigm from indirectly inferring animal body condition from foraging effort to directly measuring changes in body condition relative to foraging effort, habitat, ecological factors and anthropogenic stressors in the changing oceans. Expanding the method to account for diving air volumes will expand the system's applicability to shallower‐diving (<100 m) species, facilitating real‐time monitoring of body condition in a broad range of breath‐hold divers.