Increase In Frictional Resistance Research Articles

Artificial-intelligence-model to optimize biocide dosing in seawater-cooled industrial process applications considering environmental, technical, energetic, and economic aspects

This research introduces an Artificial Intelligence (AI) based model designed to concurrently optimize energy supply management, biocide dosing, and maintenance scheduling for heat exchangers. This optimization considers energetic, technical, economic, and environmental considerations. The impact of biofilm on heat exchangers is assessed, revealing a 41% reduction in thermal efficiency and a 113% increase in flow frictional resistance of the fluid compared to the initial state. Consequently, the pump’s power consumption, required to maintain hydraulic conditions, rises by 9%. The newly developed AI model detects the point at which the heat exchanger’s performance begins to decline due to accumulating dirt, marking day 44 of experimentation as the threshold to commence the antifouling biocide dosing. Leveraging this AI model to monitor heat exchanger efficiency represents an innovative approach to optimizing antifouling biocide dosing and reduce the environmental impact stemming from industrial plants.

Frictional Resistance Increase Due to Hull Roughness: An Analysis of the Hull Form Parameters Influence

An awareness of the drag increase brought on by biofouling's roughness on the ship hull is one technique to cut emissions aboard ship. However, predicting the increased drag on ships poses significant challenges. When predicting the rise in frictional resistance brought on by roughness, the hull is considered flat. In fact, ship hulls have a variety of shapes, and it is not certain whether this is a factor influencing the magnitude of the increase in resistance due to roughness. In this article, the effect of the hull's form parameters— (ratio of length per breadth), (coefficient block), and (Length of center buoyancy)—on the increase in frictional resistance brought on by roughness have been investigated. The method used to calculate the ship resistance is Computational Fluid Dynamics (CFD) simulation, complemented by roughness modelling using the wall function approach method. The Design of Experiment (DOE) method has been used to vary the shape of the hull model as a variation of the test specimen in this study. The verification and validation tests have been carried out on the CFD simulation results, where the results have been compared with proven empirical methods. Based on the study results, the value of frictional resistance and increased frictional resistance () of all specimens has shown no significant difference in value, evidenced by the variance values, ranging only 1.57-2.1%. Thus, these results prove that the increase in frictional resistance due to roughness is sufficient to assume the ship's hull as a flat plate. The other finding is that roughness can also increase the pressure resistance, and hull shape parameters also contribute towards changes in the value of resistance.

Numerical parametric assessment of the effects of stern wedges on the pressure and friction resistance of high-speed craft

ABSTRACT In the current study, wedge effects on a planing hull's friction and pressure resistance components have been numerically investigated. This study also assesses how the variation of pressure and friction resistance components can be predicted by trim angle variation. The obtained results indicate that at , stern wedges slightly increase the vessel's pressure resistance. By increasing the speed, pressure, and friction resistance components of the wedge-mounted model descends and increases, respectively, compared to the baseline model. The results indicate that the wedge-mounted planing hull experience a decrease in pressure resistance of up to 27% and an increase in friction resistance of up to 34%. After , some interaction effects between the wedge length and height on the total and pressure resistance appear. The findings also indicate that wedge effects on the planing hulls' pressure and friction resistance components are much different from those of displacement hulls.

Substrate effects in hysteresis of microscale Ni–Mn–Sn Heusler alloy films

During martensitic phase transformations in thin films, substrates impact hysteresis by introducing an additional interface, which can inhibit martensite/austenite interface motion. In order to reduce hysteresis, we examine 2.9–14.5 μm thick Ni–Mn–Sn films, which in some cases have been delaminated from the substrates before or after annealing. We compare thermal hysteresis and defect densities at the interface. Delaminating films prior to annealing decreases hysteresis, whereas delaminating films after annealing does not significantly impact hysteresis. Substrate effects are attributed to the thermal expansion mismatch between the film and substrate, resulting in the formation of dislocations at the interface and, consequentially, an increase in frictional resistance to martensite/austenite interface motion.

Increasing the Wear Resistance of Structural Alloy Steel 38CrNi3MoV Subjected to Isothermal Hardening and Deep Cryogenic Treatment

In the production of critical parts for various machines and mechanisms, expensive structural steels are used alloyed with chromium, nickel, molybdenum, and vanadium. In practice, the wear resistance of parts, especially under severe operating conditions, may be insufficient due to uneven microstructure and the content of retained austenite. Therefore, increasing the operational stability of various products made of alloy steels is an important task. The purpose of this work is to investigate the effect of isothermal hardening from the intermediate (γ+α)-area and the duration of deep cryogenic treatment on the structure formation and frictional wear resistance of 38CrNi3MoV steel. The isothermal hardening promotes the formation of the required multiphase microstructure of 38CrNi3MoV steel. The influence of the duration of deep cryogenic treatment on the microhardness, amount of retained austenite, fine structure parameters, and friction wear of 38CrNi3MoV steel are established. Complex heat treatment of 38CrNi3MoV steel, according to the proposed mode, makes it possible to achieve a significant decomposition of retained austenite to martensite, which leads to an increase in frictional wear resistance of ~58%.

Melting Characteristics of Hybrid Nano Enhanced Phase Change Material in a Finned Circular Tube

In this study, the melting characteristics of hybrid nano-enhanced phase change material in a finned circular tube were studied by using the Finite volume method. This setup of circular tubes with a phase change material is used as cooling systems in automotive industries, air-conditioning, refrigerators, and other applications of cooling systems. There is a need for enhancing the specific heat capacity of this system to ensure that the system works even at high temperatures. As the current problem includes many design parameters and boundary constraints, the finite volume method has been performed to obtain a detailed report and data to examine the deformation of the hybrid nanoparticles and heat transfer rate on the corresponding surface. The current paper reviews and focuses mainly on the high-temperature PCM. And the suitable PCM has been selected based on its limitations and properties. To ensure the increased specific heat capacity, a salt-based phase change material, i.e., a mixture of NaNO3-KNO3 (60:40 ratio) binary salt. This PCM could hold a temperature up to 334◦C before melting to change its phase. In addition to spherical-shaped nanoparticles of silica (SiO2) in this binary salt, it tends to have a significant potential for enhancing the thermal storage characteristics of the NaNO3-KNO3 binary salt. On an extended surface, Finns are used on the peripheral of the circular tube to increase the surface area, which leads to an increase in frictional resistance resulting in a reduced airflow rate in the vicinity of the finned surface. From case studies, it has been found that the optimum fork-shaped fin array with two branches gives higher heat dissipation than the optimum rectangular fin. In the majority of the cases, the optimum fork-shaped fin array gives a 59.9% higher heat transfer rate compared to the rectangular fin array. Thus, the melting characteristics of the hybrid of NaNO3- KNO3 with nanoparticles of silica are studied when placed in a circular tube containing fork-shaped fins.

Numerical simulation of flow resistance characteristics in a rod bundle channel under vertical and inclined conditions

Numerical simulation of flow resistance characteristics in a 3 × 3 rod bundle channel under vertical and inclined conditions is carried out. Compared with experimental results, it is verified that Reynolds stress model with enhanced wall treatment can accurately calculate flow parameters in rod bundle. Under vertical conditions, flow boundary layer at high Reynolds number is relatively thinner and radial velocity vector at interface of each sub-channel is basically parallel to dividing line or opposite direction. Mainstream velocity distribution in channel under heating conditions is more uniform and radial secondary flow is more likely to occur than that under adiabatic conditions. Axial velocity near wall is a dominated factor to determine wall shear stress. Under inclined conditions, deviation of overall flow velocity distribution is more obvious and relative intensity of natural convection is more significant at low Reynolds number conditions compared with high Reynolds number conditions. Main mechanism of increase in frictional resistance due to inclination is that natural convection caused by thermal stratification changes flow velocity distribution of each sub-channel. Additionally, natural convection increases radial secondary flow area, broadens wall shear stress distribution and also increases average wall shear stress of cross section.

Study on mechanical response of steel pipe jacking considering the effect of pipe sticking

Pipe sticking is frequently occurred during the pipe jacking in rock strata due to the blockages accumulated in the annulus gap. The frictional resistance induced by surrounding rocks increased sharply, and the total jacking force might exceed the pipe structural capacity. Through the in-situ monitoring and direct shear tests, the influence of the pipe sticking on the deformation and frictional properties of the steel pipe jacking was analyzed. In the severe pipe sticking, the contact pressure acting on the pipe exceeded 1 MPa, and significant radial compression took place. The hoop strain of the pipe contacting with the blockages illustrated a tensile state, while the pipe contacting with the slurry or groundwater exhibited compressive strain. In the direct shear tests, the frictional properties of the steel pipe-rock interface under five contact conditions were evaluated. Experimental results revealed that the pipe-rock friction coefficient under the blockages exhibited as high as 0.6, and the blockages in annulus gap were the main reason for the increase in frictional resistance. In addition, the causes of the pipe sticking were analyzed, and measures were implemented to resolve the pipe sticking issue.

CFD analysis of the increase in ship resistance due to biofouling growth represented by roughness length scale

Fuel consumption is heavily influenced by ship resistance, which mostly consists of friction resistance. During her operation, a ship is susceptible to the attachment of biofouling to its hull. The arbitrary form of biofouling induces an increase in surface roughness, which is responsible for the increase in friction resistance. This research analyses the increase in skin friction resistance due to biofouling, that is represented by a few variations of roughness length scale, in various orders throughout the models. Two-dimensional models of flat plates are utilized to investigate this issue by means of computational fluid dynamics (CFD) analysis. This study uses models with 0.56 m length to be tested in five Reynolds numbers, to be compared to a similar experiment conducted by using wind tunnel. Other models include 30 m and 60 m length to be tested in two Reynolds numbers each. It is found that the increase in skin friction reaches 3.5 – 31.4% for 0.6 m, 68.1 – 206.9% for 30 m with extreme regular roughness and 117.3 – 129.3% for 30 m with extreme irregular roughness, and 59.5 – 179.6% for 60 m with extreme regular roughness and 123.5 – 128.9% for 60 m with extreme irregular roughness.

Parameter Analysis and Optimization of Annular Jet Pump Based on Kriging Model

Jet pump efficiency heavily relies on the geometrical parameters of the pump design and parameter global optimization in the full variable space is still a big challenge. This paper proposed a global optimization method for annular jet pump design combining computational fluid dynamics (CFD) simulation, the Kriging approximate model and experimental data. The suction angle, the flow ratio, the diffusion angle, and the area ratio are selected as the design variables for optimization. The optimal space filling design (OSF) method is used to generate sampling points from the design space of the four design variables. The optimization method solves the constrained optimization problem with a given head ratio by building the functional relationship established by the Kriging model between efficiency and design parameters, which makes the method more applicable. The design result shows that the annular jet pump efficiency is predicted well by the Kriging model; m is a key variable affecting the annular jet pump efficiency. As the area ratio m decreases, the mixing effect at the suction chamber outlet can be improved, but the frictional resistance increases.

Evaluating the corollary of the interdependency of rock joint properties on subsurface fracturing

The characteristics of structural discontinuities in the subsurface environment often play a key role in the overall behaviour of such systems and their response to externally imposed conditions. Rock joints are one of such features that constitute the heterogeneity of rock masses. Akin to other forms of discontinuities, the characteristics of rock joints affect the performance of their parent rock masses, which are constituents of rock formations. The fracturing process is one of such key geo-mechanical phenomena that is inevitably influenced by pre-existing joints. A numerical technique implemented via a discrete element method (DEM) is herein adopted to evaluate two fundamental properties that control the shear and dilatancy responses of discontinuities. Though these properties are also assessed in isolation, their interdependency, which is a dominant factor, is investigated. As joint frictional resistance increases, it escalates the potential of the joint to attenuate the rate of fracture growth. On the other hand, an increase in joint dilatancy increases the intensity of fracturing. The impact of joint frictional resistance is more pronounced at high friction magnitudes, and in this range, the predominant influence of joint friction overwhelms any effect of joint dilatancy. Contrarily, at low joint frictional resistance, contributions from even a small magnitude of joint dilatancy increases the degree of fracturing. The inter-relationship between joint friction and dilatancy has influencing implications that govern the performance of rock masses. An inquiry into their combined contributions provides information prerequisite for a more accurate estimation and appraisal of fracture behaviour in underground systems.

A Study on the Change of Displacement according to the Drainage Pump Outlet Shape and Size of Combat Equipment.

Combat equipment is designed to cross the river on its own. The important thing here is that first, the inflow of water should be minimal, and the second is draining out the inside of the inflow. In this study, we have studied how to effectively discharge the incoming water. The purpose of this study is to compare the flow rate, so the pump pressure was not considered. The flow analysis was carried out only by considering the head pressure and atmospheric pressure. The outlet shape was found to have 13% more emissions than the spiral, which caused vortices due to the helical grooves and protrusions inside the hole, resulting in the loss of flow energy due to the increase in frictional resistance. As a result of checking the drainage according to the size, when the hole size is small, the drainage of water is gradually progressed. When the hole size is large, the drainage is increased rapidly and it is confirmed that it is discharged in a short time. If the hole size is infinite, the effect of drowning is maximized, but it may affect the structural strength of combat equipment, so it should be considered when designing the size of the outlet. Drainage pumps can save the combat equipment from the risk of flooding for water inflows below a certain level. Therefore, when the drainage pump is maintained, the pump is maintained, the pump efficiency should be guaranteed by thorough inspection and performance test.

Drag Penalty Causing from the Roughness of Recently Cleaned and Painted Ship Hull Using RANS CFD

The issue of global warming makes energy savings on ships compulsory. One of the biggest causes of energy waste is the increase in friction resistance due to the hull roughness that makes not hydraulically smooth. The process of cleaning and repainting the ship hull turned out to make a roughness that can provide a drag penalty. An investigation using a resolved Reynolds-averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) approached to assess the increase in ship resistance from a recently cleaned and painted ship hull roughness are reported. The rough surface was obtained through surface imprint during its annual dry-docking and digitized via a laser scanner. A roughness geometry that was obtained from the scanning was prepared for the CFD simulations. The results for two ships show that such surface would cause an increase in friction resistance of the full-scale ship by 33%-35%, which corresponds to an increase in the ship’s total resistance by 7.5%-28%. The type of ship that is mostly affected by the roughness is a ship with a higher frictional resistance ratio (lower Froude Number) compared to residual resistances, where most of them are large ships.

Numerical Study on the Hydrodynamic Performance of Antifouling Paints

This study presents a simple numerical method that can be used to evaluate the hydrodynamic performances of antifouling paints. Steady Reynolds-averaged Navier-Stokes equations were solved through a finite volume technique, whereas roughness was modeled with experimentally determined roughness functions. First, the methodology was validated with previous experimental studies with a flat plate. Second, flow around the Kriso Container Ship was examined. Lastly, full-scale results were predicted using Granville’s similarity law. Results indicated that roughness has a similar effect on the viscous pressure resistance and frictional resistance around a Reynolds number of 107. Moreover, the increase in frictional resistance due to roughness was calculated to be approximately 3%–5% at the ship scale depending on the paint.

Validation of the CFD approach for modelling roughness effect on ship resistance

Recently, there have been active efforts to investigate the effect of hull roughness on ship resistance using Computational Fluid Dynamics (CFD). Although, several studies demonstrated that the roughness modelling in the CFD simulations can precisely predict the increase in frictional resistance due to the surface roughness, the experimental validations have been made only for flat plates which have zero pressure gradient. This means that the validations cannot necessarily guarantee the validity of this method for other ship resistance components besides the frictional resistance. Therefore, it is worth demonstrating the validity of the roughness modelling in CFD on the total resistance of a 3D hull. In this study, CFD models of a towed flat plate and a KRISO Container Ship (KCS) model were developed. In order to simulate the roughness effect in the turbulent boundary layer, a previously determined roughness function of a sand-grain surface was employed in the wall-function of the CFD model. Then the result of the CFD simulations was compared with the experimental data. The result showed a good agreement suggesting that the CFD approach can precisely predict the roughness effect on the total resistance of the 3D hull. Finally, the roughness effects on the individual ship resistance components were investigated.

Time-dependent biofouling growth model for predicting the effects of biofouling on ship resistance and powering

This paper presents a time-dependent biofouling growth model which enables prediction of the effect of biofouling on ship resistance and powering for day-to-day evaluation. Initially, antifouling coating tests data were employed in the model to predict coating performance over time by considering the ship operating profile and shipping route. Based on the equivalent sand roughness heights found in literature, time-dependent biofouling growth predictions were turned into equivalent sand roughness heights. Then, the provided roughness functions for different surface conditions as well as the predicted equivalent sand roughness heights were employed in Granville's similarity law scaling to investigate the effect of roughness on full-scale ship resistance.Then, the model was tested through one-year long operation data of a 176 m long tanker measured by on-board systems to validate the model. Percentage increase in frictional resistance of the 176 m long tanker was predicted to be ~32%. Results were compared and validated using real data. Secondly, a case study was performed using noon-report data for 3-years operation of a 258 m long crude-oil carrier. Increase in effective power of the ship was predicted to be ~25%. Finally, the predictions were compared to ship performance reports that were provided by the ship operator.

Investigation of fuel consumption on an operating ship due to biofouling growth and quality of anti-fouling coating

This article will look into to the environmental and economic issues in the maritime sector that arise due to biofouling. For the shipping industry, biofouling is known to increase hull roughness that would lead to an increase in friction resistance and fuel consumption. Here we present a short review regarding ship-hull roughness due to biofouling and its associated increase in skin friction drag, and analysis of fuel consumption from an operating ship with two different anti-fouling coating. The data shows that a higher quality antifouling would result in a low biofouling attachment on the hull surface, resulting in a lower fuel consumption.

Impact of biofilm on the resistance characteristics and nominal wake

Numerical assessment of the impact of biofilm on the resistance characteristics and nominal wake is carried out within this study. Therefore, roughness function models are implemented within the wall function of the commercial software package. Extensive verification study as well as the estimation of numerical uncertainties in the prediction of the resistance characteristics and nominal wake is made. Furthermore, numerical uncertainties in the prediction of the change in resistance characteristics and nominal wake are assessed as well. Thereafter, validation study is carried out by comparing the obtained increases in the frictional and total resistance with the increases obtained using Granville similarity law scaling method. The significant impact of biofilm on the resistance characteristics as well as on the nominal wake is noted. Thus, total resistance and frictional resistance increase due to the presence of biofilm, while wave resistance decreases, contradicting the classical methods, which consider that only frictional resistance is affected due to the presence of roughness. Furthermore, nominal wake coefficient is increased due to the presence of biofilm, which causes slowdown of the flow.

Experimental Study on the Complex Contact Frictional Property of an Ultralong Distance Large-Section Concrete Pipe Jacking and Prediction of Pipe String Stuck

Line 2 of the Guanjingkou Pipe Jacking Project in Chongqing encountered a pipe sticking problem, whose occurrence was inevitably attributed to the higher total frictional resistance of pipe strings rather than the maximum jacking force. Line 1, which is about to start construction, has basically the same construction environment as Line 2 using the same microshield and pipe string sizes. To avoid repeating the pipe sticking problem of Line 2, the mutual friction characteristics between the surrounding rocks and jacked pipe strings are studied for Line 1 by adopting the same test method under seven complex contact conditions (the presence or various combinations of three substances, i.e., extrapipe string field debris, bentonite slurry, and sand-laden waste slurry, on the jacked pipe string-surrounding rock contact surface are mainly considered). The results show that sufficient bentonite slurry can effectively reduce the frictional resistance, and when the amount of bentonite is insufficient, the average friction coefficient (AFC) of the later contact surface increases by 50%∼70%. The comparison of the monitored versus predicted jacking forces indicates that the value predicted by the test is slightly higher than the monitored force and the variation trends of the two match well, thus proving the correctness of the test results. It is possible to continue predicting the variation trends of the jacking force and frictional resistance based on the contact situation outside the pipe string wall, which greatly lowers the probability of re-encountering pipe sticking. The test results not only explain the important role of bentonite slurry in reducing the pipe string wall frictional resistance but also suggest that an increase in the pipe string wall frictional resistance resulting from the complex contact inflow into the overexcavation gap is the root cause of pipe sticking; moreover, the number of jacked pipe strings matching a single IJS is the second cause of pipe string sticking. The methodology of this study can provide a reference for other studies concerning the jacking force of long-distance rock microshield tunnelling.

An investigation into the effect of biofouling on the ship hydrodynamic characteristics using CFD

To reduce the fuel consumption and green-house gas emissions of ships, it is necessary to understand the ship resistance. In this context, understanding the effect of surface roughness on the frictional resistance is of particular importance since the skin friction, which often takes a large portion in ship drag, increases with surface roughness. Although a large number of studies have been carried out since the age of William Froude, understanding the roughness effect is yet challenging due to its unique feature in scaling. In this study, a Computational Fluid Dynamics (CFD) based unsteady Reynolds Averaged Navier-Stokes (RANS) resistance simulation model was developed to predict the effect of barnacle fouling mainly on the resistance and hull wake characteristics of the full-scale KRISO container ship (KCS) hull. Initially, a roughness function model was employed in the wall-function of the CFD software to represent the surface conditions of barnacle fouling. A validation study was carried out involving the model-scale flat plate simulation, and then the same approach was applied in full-scale flat plate simulation and full-scale 3D KCS hull simulation for predicting the effect of barnacle fouling. The increase in frictional resistance due to the different fouling conditions were predicted and compared with the results obtained using the boundary layer similarity law analysis of Granville. Also, a further investigation of the roughness effect on the residuary resistance, viscous pressure resistance and wave making resistance was carried out. Finally, the roughness effect on the wave profile, pressure distribution along the hull, velocity distribution around the hull and wake flows were examined.