Resistance and Propulsion Study of a 17 500-DWT Oil Tanker Using Computational Fluid Dynamics and Slender-Ship Theory: Effects of Energy-Saving Device Fins

This paper presents the optimization of a flow injection analysis (FIA) biosensor with respect to its design and operational parameters such as flow cell geometry, microfluidic channel dimensions, and flow rate. Since it is time consuming and costly to investigate the effect of each factor on the biosensor performance by building it, computational fluid dynamics (CFD) theory is presented as a great tool for finding optimal parameter values. This modeling approach has a high potential in the design of high accuracy FIA-biosensors, regardless of the chosen enzyme substrate system. As an example the optimal design for a glucose/glucose oxidase FIA biosensor is calculated with the CFD theory

The method of two-phase flow is used to analyze the three-dimensional debris flow field via the theory of computational fluid dynamics (CFD). The theory of computational fluid dynamics and finite volume method is introduced briefly, and the rheological characteristic of non-Newtonian fluid is illuminated. The three-dimensional topography model of Niwan gully was established, and the three-dimensional debris flow field was analyzed. The values and distributions of velocity and pressure field of the debris flow have been obtained; the relationship between the shear strain rate, viscosity, and velocity was analyzed. The results suggest that it is more accurate to catch the free surface of debris flow using the method of two-phase flow. The sediment area of the Niwan gully debris flow can be estimated quickly, and it may have significance for the engineering prevention of debris flow disasters.

The majority of articles in this Special Issue illuminate various aspects of Jack Herring’s contributions to the theory of turbulence, atmospheric sciences, and computational fluid dynamics (CFD), be it through his publications, presentations, collaborations, work with colleagues and students, or personal contacts [...]

Multi-anemometer optimal layout and weighted fusion method for estimation of ship surface steady-state wind parameters

The extrusion technology of plastic profile with metal insert is recently an advanced plastic processing method whose products keeps rising today for their excellent performance. However, the related fundamental research on polymer forming mechanism in the extrusion process of plastic profile with metal insert is lagging behind. With the development of computational fluid dynamics (CFD) theory, numerical method becomes an effective way to investigate such complex material forming problems as in the polymer extrusion process. In the present study, the mathematical model for three-dimensional non-isothermal viscous flow of the polymer melts obeying a Carreau model is developed based on the CFD theory. The Williams–Landel–Ferry equation is employed to involve the temperature dependence of material parameters. A decoupled numerical algorithm based on the penalty finite element method is conducted to predict the rheological behaviors of polymer melts within the complex flow channel. The streamline upwind/Petrov–Galerkin scheme is employed to improve the computational stability for the calculation of temperature field. Based on the theoretical model, the essential flow characteristics of polymer melts in the extrusion process of plastic profile with metal insert is investigated. The distributions of principal field variables like flow velocity, melt temperature, flow stress and pressure drop are predicted. The effects of die structure parameters including the intake angle and the distribution section length upon the melts flow patterns are further discussed. The variations of melt rheological properties versus different processing conditions like the volume flow rate and the metal insert moving velocity are also investigated. Some advice on practical processing operations of the extrusion process of plastic profile with metal insert is accordingly put forward based on the numerical results.

Computational fluid dynamics is taught in many universities and is a trending elective option among engineering students. Although analyzing computational fluid dynamics simulations is exciting enough, the theory is equation intensive, sometimes very abstract and also difficult to visualize for the novice. A creative thinking based approach termed synectics, which involves analogies, was therefore applied in classroom teaching to increase student comfort with the equations. For this purpose six analogies encompassing basic computational fluid dynamics concepts were developed along with pictorial representations, and are presented in this work. These analogies were integrated into classroom teaching via synectics procedures. Student feedback was positive and reflected higher engagement with the course compared to when the metaphoric activity was not implemented. This work attempts to demonstrate the feasibility and value of applying creative techniques, even when teaching a highly structured and equation oriented course such as computational fluid dynamics.

Marine centrifugal pump is one of the important factors that cause ship vibration, so the research on centrifugal pump vibration is particularly important. In this paper, in order to study the flow-induced vibration characteristics of centrifugal pump, a virtual prototype model of the centrifugal pump is established in finite element method. The theory of Computational fluid dynamics (CFD) is utilized to analyze the inner flow field of the centrifugal pump, and steady-state calculation and transient calculation of the flow field are completed. The fluid forces acquired from the transient calculation results of flow field are used as the excitation loads for the virtual prototype model of the centrifugal pump. The fluid-solid coupling model of the centrifugal pump is built, and the vibration acceleration of the centrifugal pump's foot is calculated, and the flow-induced vibration characteristics of the centrifugal pump are obtained. The data of the centrifugal pump measured in the experiment are consistent with the simulation results. This study provide reference for the fluid-solid coupling method in centrifugal pump fluid field prediction and flow-induced vibration research.

Based on the theory of computational fluid dynamics (CFD), an integrated numerical model of the positive pulse generator with the upstream and downstream pipeline was established. Compared with the previous numerical simulation, this model can simulate the generation and transmission process of positive pulse signals efficiently and accurately for the first time. Based on the mechanical structure of the common positive pulse generator, the simplified two-dimensional axisymmetric geometric model of the flow region was established considering its flow symmetry characteristics. Combined with dynamic mesh and sliding mesh technology, the reciprocating motion of the valve is simulated, and a custom function controls the motion to generate low-frequency pulse signals. Comparing the new CFD model with the previous numerical model, it is found that with the periodic change of flow area, compression wave, and expansion wave are generated simultaneously in the upstream and downstream of the positive pulse, with the same frequency and opposite phase, which satisfies the transient hydrodynamics theory. Meanwhile, as the pressure wave propagates, the irregular pulse waveform becomes sinusoidal, and its amplitude decreases gradually. This paper presents a new CFD numerical model and simulation scheme, which can provide an efficient and accurate method for designing and simulating a mud pulse telemetry system. INTRODUCTION With the development of the global oil and gas exploration and development objects in the direction of "ultra-deep formation, unconventional formation, old development formation," the scale of horizontal wells has increased significantly, and there are many complex underground conditions (Antunes et al., 2015; Mwachaka et al., 2018). We need to integrate logging and measuring while drilling (LWD and MWD), downhole control, and big data analysis in real-time to solve the problems encountered during drilling and completion. As a wireless data transmission mode, mud pulse telemetry (MPT) has a long transmission distance, good economy, and wide application range (Jia et al., 2018; Chin et al., 2014). Among them, a positive pulse is developed earliest, with stable transmission and strong anti-interference ability.

The unbalanced flow problem often occurs at die exit in the extrusion process of plastic profile, which directly influences the performance of final products. For the lack of corresponding theoretical basis, reasonable extrusion die design is still a difficult task, especially for the complex hollow profile. With the development of computational fluid dynamics theory, numerical method becomes an effective way to investigate the complex material forming problems. In the present study, a design strategy for complex hollow profile extrusion die was proposed based on the principles of flow balance. The mathematical model for three-dimensional non-isothermal polymer melt flow within complex extrusion die runner was developed based on the computational fluid dynamics (CFD) theory. The governing equations were deduced based on the finite volume method, and the pressure-velocity coupling problem was solved by using the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm. The Arrhenius equation was employed to involve the temperature dependence of material parameters. The flow characteristics of PVC polymer melts in the extrusion process of complex hollow profile were investigated. The distributions of principal field variables including flow velocity, melt temperature, and pressure drop were obtained. The effects of die geometric parameters on the velocity distribution uniformity were further analyzed, and a design strategy was proposed to achieve the flow balance in complex plastic profile extrusion process.

Solute mixing at the cross junction was assumed to be instantaneous and completely mixed in initial water quality models of water distribution system. With recent developments, some computational simulations and experiments verified an incomplete mixing state at cross junctions, which affected the accuracy of water quality model in water distribution networks. This paper, by the theory of computational fluid dynamics, confirms incomplete mixing at the pipe intersections. At the cross of pipe network, the forward direction of the fluid particle is directly related to water momentum. A mixing model at the cross in water supply networks is established to improve the water quality model and the simulation accuracy. For the potential of accidental or intentional contamination events, it makes a powerful prediction. This study is working to prevent and prepare for terrorist attacks, minimize public health impacts and infrastructure damage, and enhance recovery.

We introduce a paradigm shift for developing parameterizations of subgrid motion in numerical weather prediction (NWP) models, which is based on recent developments in the theory of computational fluid dynamics.  The governing equations of an NWP model are based on the same Navier-Stokes (N-S) equations used in computational fluid dynamics.  They must be averaged over a grid-cell volume before transforming into discrete forms in order to be solved numerically.  Consequently, extra terms of turbulent subgrid motion appear in these governing equations that must be approximated or parameterized.  The recent development of the formal theory on the N-S equations filtered via numerical discretization concludes that such parametrizations cannot be exact for the equations to be solvable numerically.  Approximation in these parameterizations is necessary for the N-S equations to be solvable as a well-posed problem.  Practically, this has two implications for parameterizing subgrid motion in NWP models.  First, the development of the parameterizations of subgrid motion is required to be driven by improving the accuracy of the parameterizations to address specific prominent performance issues of an NWP model, and the improvement should be based on observations of forecast variables and subgrid processes for it to be physically relevant.  Second, the parameterizations should be as simple as possible for feasible performance tuning based on observations and for computational efficiency.  In this presentation, we will use two examples to discuss what the problem-driven and observation-based approach means in developing subgrid convection and turbulent mixing parameterizations in NWP models.  We will use the two examples to advocate that the problem-driven and observation-based approach should be used to develop all subgrid physics parameterizations in weather and climate models for developing parameterizations of subgrid motion.

(1) Background: Previous studies have compared research into ski jumping in different motor processes, but there is a lack of comparative analysis of the biomechanical research methods used to investigate different ski jumping sports. (2) Content: Our study compared the advantages and disadvantages of six research methods and proposes future research directions. Motion video collection and analysis show that controlling angular momentum and achieving stable flight attitude in the take-off process are the most critical factors in ski jumping performance. Most research on force platforms focuses on dynamic performance at the time of take-off, but there are few training sites with an embedded force platform, and so, more empirical research is required. Wearable inertial measurement units, including gyroscopes and accelerometers, can be used to determine a series of forces, calculate the joint angle, and speculate the position of the centroid during motion. Surface EMG studies are primarily used to compare the activity characteristics of the lower limb muscles in the actual field of the jump, the exercise simulation, and the lack of complete training process data. Wind tunnel measurement can satisfy fluid mechanics simulation experiments and provide theoretical support for optimizing special ski jumping technology. Based on the theory of computational fluid dynamics, the optimal drag reduction posture data of ski jumpers can be derived using computer simulations. (3) Conclusions: Due to the wide range of ski jumping sports, the present research focused on the kinematics and dynamics of different movement stages, lacking the study of the complete exercise training process. The range of wearable inertial measurement and sensor equipment can cover the whole process of ski jumping, including kinematics and dynamics data, and is a feasible and reliable test method for monitoring ski jump training in natural environments. The simultaneous testing of surface electromyography, kinematics, and dynamics requires further exploration. (4) Future direction of development: Under computational fluid dynamics, wearable inertial measurement units and global navigation satellite systems (GNSSs), intelligent wind tunnel experimental training areas will become essential tools for ski jumping research.

This paper combined the school-enterprise cooperation project, based on the theory of computational fluid dynamics (CFD), and has completed the simulation of fluid flow field characteristics in the engagement process of wet clutch through the flow field simulation software FLUENT, which has a certain theoretical and practical significance to improve the performance of the wet clutch.

The coolant flow field distribution affects the cooling effect of internal combustion (IC) engine. Simulated calculation is applied in the engine water jacket structure design process more and more because the method can predict the complex flow phenomena in the engine cooling water jacket. In order to summarize the design experience for the separate type water jacket, many kinds of improved 3D models are set up. The simulated calculation experiments are carried out based on the theory of computational fluid dynamics (CFD). The influence of flow guide structure on distribution of flow field is analyzed and summarized. The results indicate that the correct use of the convex surface and the bars can guide the coolant and the flow field can be improved and optimized.

In this paper, the mathematical model of the flow filed in centrifugal compressor of turbocharger was studied. Based on the theory of computational fluid dynamics (CFD), performance curves and parameter distributions of the compressor were obtained from the 3-D numerical simulation by using CFX. Meanwhile, the influences of grid number and distribution on compressor performance were investigated, and numerical calculation method was analyzed and validated, through combining with test data. The results obtained show the increase of the grid number has little influence on compressor performance while the grid number of single-passage is above 300,000. The results also show that the numerical calculation mass flow rate of compressor choke situation has a good consistent with test results, and the maximum difference of the diffuser exit pressure between simulation and experiment decrease to 3.5% with the assumption of 6 kPa additional total pressure loss at compressor inlet. The numerical simulation method in this paper can be used to predict compressor performance, and the difference of total pressure ratio between calculation and test is less than 7%, and the total-to-total efficiency also have a good consistent with test.