Computational Fluid Dynamics CFD Research Articles

CFD Analysis of Improving Air Conditioning System Performance By Adding SiO2 Nanoparticles To The Compressor Oil

The overall performance of air-conditioning systems is necessary to evaluate the comfort conditions and equipment life. in order not to varnish energy. The aim of this study is to improve performance of air conditioning by adding nanoparticles to oil of compressor. The research applied computational fluid dynamics CFD to simulate the use of SiO2 nanoparticles in air-conditioning systems. Silicon dioxide (SiO2) nanoparticles have better thermal properties than pure oil and can also significantly enhance the performance of compressor oils as well as heat transfer capability in HVAC systems. This research investigates the reactions between (0.1%, 0.4%, and %0.7) of SiO2 nanoparticles with compressor oil, to determine their impacts on heat dissipation, lubricant efficiency as well as performance overall. Results show that the addition of nanoparticles to the oil lubricant increases the COP of the air conditioning system.

Numerical and Experimental Investigation of the Aerodynamic for the IceWind Blades VAWT

The main aim of the present work is the numerical and experimental investigation carried out in, for the IceWind blade type with two heights (Model 1=250 mm) and (Model 2=125 mm). In this study a computational fluid dynamic CFD is used to simulate the aerodynamic characteristics modelled medals at 10 m/s. The finite volume method and SST (k-ω) turbulent model were used in this simulation. In the experimental part the models are manufactured by three dimensions printing machine (3D printing) using Polylactic acid (PLA), and the experimental work was implemented by using low speed wind tunnel that is available at University of Baghdad/College of Engineering/Mechanical Engineering Department/Fluid Mechanics Laboratory. The finding results from the numerical simulation show that the maximum static pressure at (Model 1) was 69.39 (pa) and the maximum velocity was 13.5 (m/s). For (Model 2) it was 62.58 (pa) and the maximum velocity was 12.69 (m/s). The minimum static pressure at (Model 1) was -66.69 (pa) and the minimum velocity was 1.04 (m/s). For (Model 2) it was -47.94 (pa) and the minimum velocity was 0.98 (m/s). The experimental results showed that (Model 1) give high performance in comparison with (Model 2) , because rotational speed 610 RPM and the power coefficient was 0.0688 also the tip speed ratio was 0.4533, when (Model 2) give rotational velocity were 265 RPM and the power coefficient was 0.03551 also the tip speed ratio was 0.2601.

Fostering Design for Sustainability through the Adoption of Computer-Aided Engineering Tools in the Development of Energy-Related Products

The main challenge to face in the development of energy-related products is represented by the adoption of effective design for sustainability strategies that encompasses the adoption of engineering design tools, knowledge collection, and reuse/sharing in technical departments. This present paper proposes an engineering design for sustainability methodology that assists engineers in developing energy-related products in compliance with ecodesign standards. The methodology uses virtual prototyping tools to assess energy consumption in compliance with energy labeling directives and analyze different use scenarios. The results obtained by numerical simulations (e.g., Finite Element Method—FEM, Computational Fluid Dynamics—CFD) are used to create specific design eco-knowledge in the field of energy-related products. Numerical results are linked with design configurations to understand the benefits introduced by engineering design choices. This knowledge is stored in a structured database with the aim of being reused when a new product is developed or improved/upgraded. The case study of an induction hob, belonging to the household appliance product family, is investigated to understand the potential and drawbacks of the presented approach in a real application. The results show that potential energy and environmental performance benefits are achieved (e.g., reduction of energy losses, achievement of A+ energy class, and overall life cycle environmental impact reduction). Additionally, a new set of ecodesign guidelines are defined for this product family and employed in developing new compliant products belonging to the same family.

Analysis of the aerodynamic performance of truck semi-trailers

In the last time, trucks have shown a very high interest in terms of their technical and fuel consumption performance. Prioritizing the phenomenon of having trucks that transport as much, as quickly and as economically as possible, this represent a new challenge for industry and engineering, which are in continuous development. The attempt to create a bridge as stable as possible between technical and consumer performance is supported by the multitude of areas that, based on studies and experimental trials, allow optimization without interfering, substantially, with the actual transport of the goods (loading capacities and transport). The main objective of this paper is to present the possibility of improving the aerodynamic performance of trucks, focusing on semi-trailers. For this study, a truck modelled at one to one scale was used, whose aerodynamic performance was verified in the virtual environment (CFD–Computational Fluid Dynamics); this environment has the possibility to test several geometric models without requiring the layout of a vehicle in physical form. To check the performance, a basic model was created, a conventional truck (tractor unit with semi-trailer), to which various semi-trailer modifications were made, such as: total and partial coverage of the side areas, idea to create a more aerodynamic profile of the semi-trailer in the back and the addition of fairings under the platform (underbody of the semi-trailer). The results describe the impact these elements have and allow the visualization of the possible future profile that is as aerodynamic as possible for semi-trailers (therefore also for trucks) from both theoretical and technical point of view. Through the proposed improvements the capacity and the transport of the goods is not affected, in a significant way so it can be said that there is the possibility of implementation in the industry.

Modelling solar water desalination system using natural convection

In recent times, solar energy has emerged as one of the most promising energy sources. Numerous scholars and researchers are exploring various applications of solar energy. This presented work focused on solar water desalination system to evaluate its thermal performance in natural convection mode. Three-dimensional Computational fluid dynamics CFD model is built in Comsol Multiphysics 6.1. Numerical model simulations have been carried out by using Heat transfer in Solid &Fluid and Laminar flow interfaces. The surface temperature varies between 19.5℃ and 102℃ while the velocity magnitude was between 0.05 m/s and 0.5 m/s. Variations of the surface temperature, velocity magnitude, pressure, convective and conductive heat flux magnitudes in Solar water desalination system are presented in the discussion section of the article.

Simulation and Experimental Investigation of Performance and Flow Behavior for Steam Ejector Refrigeration System

The ejector refrigeration system is a desirable choice to reduce energy consumption. A Computational Fluid Dynamics CFD simulation using the ANSYS package was performed to investigate the flow inside the ejector and determine the performance of a small-scale steam ejector. The experimental results showed that at the nozzle throat diameter of 2.6 mm and the evaporator temperature of 10oC, increasing boiler temperature from 110oC to 140oC decreases the entrainment ratio by 66.25%. At the boiler temperature of 120oC, increasing the evaporator temperature from 7.5 to 15 oC increases the entrainment ratio by 65.57%. While at the boiler temperature of 120oC and the evaporator temperature of 10oC, increasing the nozzle throat diameter from 2.4 to 2.8 mm decreases the entrainment ratio by 40%. The numerical results showed that reducing the condenser back pressure or increasing the primary fluid temperature, secondary fluid temperature, and nozzle throat diameter moves the second shock waves in the downstream direction. It could be concluded that the second shock series position detects the ejector operation mode. The ejector runs in critical mode if the second shock series position is close to the diffuser. In contrast, if the second shock series position moves toward the upstream, the ejector runs in subcritical mode.

Control of Propagation of Salt Wedge by using Roughness Blocks having Different Inclination

The hydraulic conditions of a flow previously proved to be changed when placing large-scale geometric roughness elements on the bed of an open channel. These elements impose more resistance to the flow. The geometry of the roughness elements, the numbers used, and the configuration are parameters that can affect the hydraulic flow characteristics. The target is to use inclined block elements to control the salt wedge propagation pointed in most estuaries to prevent its negative effects. The Computational Fluid Dynamics CFD Software was used to simulate the two-phase flow in an estuary model. In this model, the used block elements are 2 cm by 3 cm cross-sections with an inclined face in the flow direction, with a length of their sides 2 and 3 cm. These elements were placed with a constant spacing in two rows at a distance from two sides of the bed of the channel model. Six simulation runs were conducted with two different discharges and three different inclinations of the centerline of the element concerning the flow direction. The applied discharges are 30 and 45.3 l/min, and the inclination of roughness elements are 15o, 30o, and 45o. The spacing between elements in each row is kept at 3cm. The results showed that when no roughness elements were used, the propagation of the salt wedge extended to 3.9m and 3.1m at a discharge of 30 l/min and 45.31/min, respectively. The propagation of the salt wedge was reduced when using the inclined blocks roughness element. This reduction depends on the applied discharge and the angle of inclination. At the minimum applied discharge of 30 l/min, the propagation of the salt wedge was reduced by 74% at 45o inclination. In contrast, it was 69% at 30o and 64% at 15o inclination at the same discharge. When the discharge is 45.3 l/min, the propagation of the salt wedge was reduced by 85% at 45o inclinations of roughness, 84% at 30o. It was 70% at 15o inclinations. The roughness elements improve the flow turbulence that disperses and slows the salt wedge propagation beneath the fresh water.

Optimization of the thermal management system of battery thermal network model based on coupled liquid cooling of phase change materials

Battery optimization models can extend battery life, improve safety, and maximize battery performance. Previous optimization methods focus more on (Computational Fluid Dynamics) CFD and data mining. However, the two optimization methods apply only to specific battery module structures. In addition, previous studies have focused more on improving optimization algorithms to improve performance, but the computational design of large-scale battery thermal management systems still requires large loads. This paper presents a new optimization method based on the thermal equivalent circuit model (TECM) of battery thermal management system (BTMS) for the efficient design of liquid-cold coupled phase change material BTMS (PCM). The method can easily change and optimize the battery module structure according to different application scenarios. Compared with the reference structure, the TECM Parto solution optimized combined with multi-objective particle swarm optimization (MOPSO) saved 39.51 % of the liquid cooling energy consumption, reduced the maximum temperature rise of BTMS by 0.38 °C, and reduced the maximum temperature difference by 19.81 %. The method adopted can improve the efficiency and quality of BTMS design, reduce the cost of trial and error, and speed up the design process.

Semi-analytical and CFD formulations of a spherical floater

Today, humanity is facing the great pressure of fossil fuels exhaustion and environmental pollution. This obliges governments and industries to make accelerated efforts on producing green energy. The focus is spotted on marine environment which is a vast source of renewable energy. Among several classes of designs proposed for wave energy conversion, spherical Wave EnergyConverters (WECs) have received considerable attention. The problems of water wave diffraction and radiation by a sphere has been examined by a substantial amount of literature, i.e., [1]–[4], whereas in [5]–[8] linear hydrodynamic effects on a spherical WEC have been examined. All these research works are based on potential flow methodologies. Nevertheless, overthe last decade there has been a significant interest on Computational Fluid Dynamics CFD modelling due to its detailed results, focusing also to spherical WECs [9]–[10].In the present work a semi-analytical model is applied to solve the wave radiation problem around a spherical WEC (Figure 1), in the context of linear potential theory. The outcomes of the theoretical analysis are supplemented and compared with high fidelity CFD simulations (Figure 2 for a semi-submerged sphere). Furthermore, the two methodologies are compared with a theoretical approach for the hydrodynamic analysis of floating bodies with vertical axis as being presented in [11]. The method is based on the discretization of the flow field around the body using coaxial ring elements, which are generated from the approximation of the sphere’s meridian line by a stepped curve.Numerical results are given from the comparison of the three formulations, and some interesting phenomena are discussed concerning the viscous effects on the floater.
 [1] Havelock, T. H. 1955. Wave due to a floating sphere making periodic heaving oscillations. R. Soc. London,A231, 1-7.[2] Hulme, A. 1982. The wave forces acting on a floating hemisphere undergoing force periodic oscillation. J. FluidMech., 121, 443-463.[3] Wang, S. 1986. Motions of a spherical submarine in waves. Ocean Engng., 13, 249-271.[4] Wu, G.X. 1995. The interaction of water waves with a group of submerged spheres. Appl. Ocean. Res., 17, 165-184.[5] Srokosz, M.A. 1979. The submerged sphere as an absorber of wave power. J. Fluid Mech., 95, 717-741.[6] Thomas, G.P., Evans, D.V. 1981. Arrays of three-dimensional wave energy absorbers. J. Fluid Mech., 108, 67-88.[7] Linton, C.M. 1991. Radiation and diffraction of water waves by a submerged sphere in finite depth. Ocean Engng.,18, 61-74.[8] Meng, F., et al. Modal analysis of a submerged spherical point absorber with asymmetric mass distribution.Renew. Energy 130, 223-237.[9] Shami, E.A., et al. 2021. Non-linear dynamic simulations of two-body wave energy converters via identificationof viscous drag coefficients of different shapes of the submerged body based on numerical wave tank CFD simulation.Renew. Energy, 179, 983-997.[10] Katsidoniotaki, E., et al. 2023. Validation of a CFD model for wave energy system dynamics in extreme waves.Ocean Engng., 268, 113320.[11] Kokkinowrachos, K., et al. 1986. Behaviour of vertical bodies of revolution in waves. Ocean Engng., 13, 505-538

Investigation of the Different Models of Elliptical-Lopac Gate Performance under Submerged Flow Conditions

The effect of the elliptic ratio on the hydraulic performance of the LOPAC gate has been investigated using experimental and Computational Fluid Dynamics CFD simulations (Flow-3D Hydro). Experiments and simulations were carried out at three different flow discharges, three different submerged ratios, and five different elliptic ratios. In this context, the CFD model was first calibrated and verified using the measured data, and then CFD simulation was performed. The ratio of upstream/downstream flow depth, the flow discharge coefficient, and the energy dissipation through the gate have been calculated and analyzed, and the three-dimensional features of the flow have been described. Based on the results, the elliptical LOPAC gates with circular weirs determine extreme values of the controlled flow parameters. Asymmetric recirculation downstream of the gate is sometimes observed in the model predictions. The use of Coriolis coefficients relevant to the entire cross-section, here deployed just for the circular and the traditional rectangular Lopac gates, has allowed a concise way to report and compare complex flows for any experimental condition.

Thermoacoustic Combustion Stability Analysis of a Bluff Body-Stabilized Burner Fueled by Methane–Air and Hydrogen–Air Mixtures

Hydrogen can play a key role in the gradual transition towards a full decarbonization of the combustion sector, e.g., in power generation. Despite the advantages related to the use of this carbon-free fuel, there are still several challenging technical issues that must be addressed such as the thermoacoustic instability triggered by hydrogen. Given that burners are usually designed to work with methane or other fossil fuels, it is important to investigate their thermoacoustic behavior when fueled by hydrogen. In this framework, the present work aims to propose a methodology which combines Computational Fluid Dynamics CFD (3D Reynolds-Averaged Navier-Stokes (RANS)) and Finite Element Method (FEM) approaches in order to investigate the fluid dynamic and the thermoacoustic behavior introduced by hydrogen in a burner (a lab-scale bluff body stabilized burner) designed to work with methane. The case of CH4-air mixture was used for the validation against experimental results and benchmark CFD data available in the literature. Numerical results obtained from CFD simulations, namely thermofluidodynamic properties and flame characteristics (i.e., time delay and heat release rate) are used to evaluate the effects of the fuel change on the Flame Response Function to the acoustic perturbation by means of a FEM approach. As results, in the H2-air mixture case, the time delay decreases and heat release rate increases with respect to the CH4-air mixture. A study on the Rayleigh index was carried out in order to analyze the influence of H2-air mixture on thermoacoustic instability of the burner. Finally, an analysis of both frequency and growth rate (GR) on the first four modes was carried out by comparing the two mixtures. In the H2-air case the modes are prone to become more unstable with respect to the same modes of the case fueled by CH4-air, due to the change in flame topology and variation of the heat release rate and time delay fields.

Numerical simulation of gas-liquid interface in high-pressure water-blowing chamber

The load on the water chamber increases with the pressure level and blowing rate of the system, and the demand for theoretical and experimental studies related to the quantitative parameters of water chamber blowing safety becomes more and more frequent. In this paper, CFD computational fluid dynamics method is used to carry out the dynamics modeling and simulation of three-dimensional non-constant gas-liquid two-phase internal flow field of the test water chamber and the actual water chamber blowdown process to obtain the dynamic distribution of flow parameters in the water chamber under different working conditions. The results found that to ensure the safety of the water tank, as long as to ensure that the high-pressure air into the water tank at the end of the first two stages, the “bubble” movement process always does not interfere with the bulkhead, you can ensure that the high-pressure air in the water tank in the free expansion and gravity floating state, the water tank pressure will be only slightly higher than “gas - water cross-section” of the static pressure, at this moment the water chamber safety.

РАЗРАБОТКА МЕТОДА НЕИНВАЗИВНОГО ИЗМЕРЕНИЯ РАСХОДА ЖИДКОСТИ И ГАЗА ЧЕРЕЗ СТЕНКУ ТРУБОПРОВОДА

In connection to methods developed for determining “liquid-gas” volume-mass parameters, carried out at South Ural State University, this article presents a new method for measuring liquid and gas flow rates. The method makes it possible to measure a turbulent flow’s convective velocity through a pipeline wall and the volumetric flow rate of a liquid or gas. A brief description of Taylor's “frozen turbulence” hypothesis, which forms the basis of the method, is given, and the main problems associated with its proof in relation to the problem of determining the convection velocity of turbulence are identified. A mathematical signal processing method is presented based on two-dimensional frequency-wave number spectral processing and spatiotemporal signal filtering. A functional scheme and the input signal processing algorithm of the proposed device is presented. Mathematical modeling was performed in the ANSYS CFD computational fluid dynamics package using the hybrid eddy-resolving turbulence model SBES to determine the optimal configuration of the experimental setup. A brief description is given of the non-invasive sonar flow meter “K-Omega P1” prototype based on method presented and of numerical simulation results. Tests were performed on the METRAN-UPA-2000 flow test workbench which is a secondary standard. Full-scale test results on the flow test workbench for five flow rates are presented. Conclusions are drawn about the research results to date and further steps to improve the measurement method using the k-omega beamforming processing method.

CFD Study on Hydrodynamic Performances of a Planing Hull

The scope of the present study is to investigate the effects of various geometrical hull features, such as tunnels, spray rails and whiskers on the hydrodynamic performance of a high-speed planing hull. The criteria being tested to emphasize the boat performance are the total drag, sinkage and trim angle. In addition, the decomposition of the resistance into viscous and wave-making resistance are taken into consideration. The study starts with a validation test against experimental data in order to accentuate the capability of the Computational Fluid Dynamics CFD simulation to accurately predict the total drag and trim angle of the initial form. This is later followed by a verification study based on the Richardson Extrapolation method with a grid- and time-step-convergence test in order to predict the numerical errors during the simulation. After establishing the simulation parameters regarding the proper grid size and time step, the comparative study takes place for five hull shapes and two whisker configurations while the boat is sailing at eight different speeds. The assessment of the hydrodynamic flow parameters is evaluated compared to the initial form in order to investigate the influence of the geometry change on the hydrodynamic performances of the boat. Validation of the numerical results showed the reliability of the CFD simulation to accurately predict the drag and trim angle of the boat, while the comparative study revealed that the total drag can be reduced by up to 9%, especially at higher speeds.

Performance Against Cavity Index and Discharge Coefficient between Broad and Sharp Crested Weirs

The purpose of this research is examining the performance of rectangular broad and sharp crested weirs in terms of cavity index and discharge coefficient. For this purpose, a computational fluid dynamics CFD code FLUENT is applied. Firstly, the code verified by applies on the experiments work of Hagre et al 1994 the results show excellent agreements between CFD and Hager et al 1994. Secondly the code applied on both broad and sharp crested weirs. The results demonstrate that broad crested weirs have a lower discharge coefficient than sharp crested weirs, implying that broad crested weirs have a lower ability to discharge flow than sharp crested weirs. While the cavity index of a broad crested weir is lower than that of a sharp crested weir, the risk of cavitation is lower for a broad crested weir. Finally, designers should use caution when deciding which type of crest to use in their designs.

CFD modeling of petcoke co-combustion in a real cement kiln: The effect of the turbulence-chemistry interaction model applied with K-ϵ variations

Abstract Using alternative fuels (AF) in industry high consuming energy where fossil fuels are largely consumed may be a great solution to decrease CO2 emission and cost production. Or, when using these alternative fuels, the combustion may be difficult to control regarding the different components of AFs compared to fossil fuels. In this case, the use of the computational fluid dynamics CFD tools is a great solution to predict the AFs combustion behavior. This paper represents a computational study of petcoke and olive pomace (OP) co-combustion in a cement rotary kiln burner, established on the commercial CFD software ANSYS FLUENT. This study presents a useful key to choose an adequate simulation model that well predicts co-combustion problems. The performance of the K-ϵ turbulence models varieties (standard, Realizable, and Re-Normalization Group) combined with the hybrid finite rate/eddy dissipation model and the simple eddy dissipation model for predicting the co-combustion characteristics was investigated. The particle phase solutions are obtained using the Lagrangian approach. The performance of the mentioned model was evaluated based on the mesh accuracy, convergence time, temperature shape, and important chemical elements concentration. The predicted values of species concentrations and temperature are compared to the results obtained from the real case study and available literature. The standard K-ϵ model combined with the hybrid finite rate/eddy dissipation model gives the best results and the lower computational resources required for the 2-D model realized.

Study of Biodiesel Production Fluid Flow Patterns in LPD Type Static Mixing Reactors Using CFD Simulation for Sustainable Energy

Flow patterns can be analyzed accurately using a computational fluid dynamics model approach or CFD. The purpose of this study was to examine the pattern of fluid flow, pressure drop, fluid viscosity and FAME results in biodiesel production in a low pressure drop (LPD) static mixing reactor. The CFD method has three important stages, namely pre-processing (experimental data), solution search (boundary conditions and calculations) and post-processing (data presentation and validation). The simulation results show that the flow pattern occurred in turbulent flow with Reynolds number in each reactor above 3000 (Re > 3000). This research also produces a scenario that can reduce the pressure drop in the flow by performing a hole addition scenario, that successfully reduces the pressure drop by 5.13% compared to conventional LPD. Observations also show a decrease in viscosity in the hollow scenario with a decrease of 9.8% better than conventional LPD and an increase of 0.33% FAME in the scenario of adding holes. This study on biodiesel production can help increase the yield of better biodiesel with high quality and for the future can reduce or replace the use of non-renewable fossil fuels with renewable fuels so that the environment will remain sustainable.

Numerical determination of bubble size distribution in Newtonian and non-Newtonian fluid flows based on the complete turbulence spectrum

Gas-liquid mass transfer in non-Newtonian fluids is a crucial aspect of the bioprocess industry. Mass transfer is analyzed using the coefficient kLa, which is limited by the rheology since it exerts a barrier to the fluid deformation, significantly affecting the oxygen diffusivity and the bubble breakup and coalescence. However, the traditional mathematical expressions to model the bubble size distribution from bubble breakup and coalescence in turbulent flows of Newtonian fluids are restricted to the inertial sub-range of turbulence where the kinetic energy is dominated only by the microscales. Application of the Newtonian models to non-Newtonian fluids could result in inaccurate predictions by not considering the continuous phase rheology. The main goal of this research is the numerical determination and experimental comparison of bubble sizes in different axial positions of a bioreactor stirred by a Rushton turbine. Emphasis was placed on the viscosity effects on simulating bubble dispersion in a Newtonian fluid (water) and its comparison with a non-Newtonian fluid (0.4 % CMC). The mathematical framework is constructed by coupling the hydrodynamics (through computational fluid dynamics CFD) and bubble breakup and coalescence from a turbulence perspective using the complete energy spectrum that considers the contributions from the energy containing, inertial, and dissipation sub-ranges. This is achieved by including the second-order structure–function. The results of bubble sizes and kLa were compared with experimental data, and acceptable agreement was achieved. Therefore, it is shown that the viscous effects were captured numerically by the entire energy spectrum and improved the predictions of the kLa and bubble sizes compared to the traditional structure function turbulence models.

A Pipeline for the Generation of Synthetic Cardiac Color Doppler.

Color Doppler imaging (CDI) is the modality of choice for simultaneous visualization of myocardium and intracavitary flow over a wide scan area. This visualization modality is subject to several sources of error, the main ones being aliasing and clutter. Mitigation of these artifacts is a major concern for better analysis of intracardiac flow. One option to address these issues is through simulations. In this article, we present a numerical framework for generating clinical-like CDI. Synthetic blood vector fields were obtained from a patient-specific computational fluid dynamics CFD model. Realistic texture and clutter artifacts were simulated from real clinical ultrasound cineloops. We simulated several scenarios highlighting the effects of 1) flow acceleration; 2) wall clutter; and 3) transmit wavefronts, on Doppler velocities. As a comparison, an "ideal" color Doppler was also simulated, without these harmful effects. This synthetic dataset is made publicly available and can be used to evaluate the quality of Doppler estimation techniques. Besides, this approach can be seen as a first step toward the generation of comprehensive datasets for training neural networks to improve the quality of Doppler imaging.

Hydrodynamic Characteristics of Remora’s Symbiotic Relationships

Symbiotic relationships have developed through natural evolution which can provide advantages to parties in terms of survival. For example, that of the remora fish attached to the body of a shark to compensate for their poor swimming ability. From the remora's perspective, this could be associated to an increased hydrodynamic efficiency in swimming and this needs to be investigated. To understand the remora's swimming strategy in the attachment state, a systematic study has been conducted using the commercial Computational Fluid Dynamics CFD software, STAR-CCM+ to analyse and compare the resistance characteristics of the remora in attached swimming conditions. Two fundamental questions are addressed: what is the effect of the developed boundary layer flow and the effect of the adverse pressure gradient on the remora's hydrodynamic characteristics? By researching the hydrodynamic characteristics of the remora on varying attachment locations, the remora's unique behaviours could be applied to autonomous underwater vehicles (AUVs), which currently cannot perform docking and recovery without asking the mother vehicle to come for a halt.