Cross-sectional Shape Research Articles

Warren truss inspired hierarchical beams for three dimensional hierarchical truss lattice materials

Networks of beams are a subject of increasing interest to create architected materials with exceptional mechanical properties and low density. This paper investigates the mechanical properties of one dimensional (1D) hierarchical beams for the development of three dimensional (3D) truss lattice materials. These 1D hierarchical beams are constructed in two configurations by placing axial and inclined struts in single and double laced Warren truss patterns in each side of a beam with polygon cross section. Analytical and numerical analyses have been used to characterize their mechanical properties, including the elastic modulus, second moment of area, and shear stiffness of hierarchical beams drawn from a broad design space. Also, the failure limits of the beams with respect to parent material failure and various buckling modes are probed. Finally, the hierarchical beams have been implemented as the constituent members of Kelvin and octet lattices, and the elastic modulus and failure boundaries of the second-order hierarchical lattices are evaluated. The investigation reveals the competition between the elastic properties in the individual hierarchical beams based on different combinations of the design variables. The stiffness of the designs under compression and bending is found to be a function of the axial member size and cross sectional shape of the hierarchical beam. On the other hand, the shear stiffness of hierarchical beam designs is a function of the inclined member size and their inclination angle. It is demonstrated that incorporating hierarchy in the Kelvin and octet truss lattices can enhance the load bearing capacity of designs at low relative densities when compared to their hollow counterparts. Also, it is shown that second-order hierarchical stretching and bending-dominated lattices incorporating first-order hierarchical beams, can not only achieve but also surpass the strength and stiffness scaling relations established for first-order lattices. This becomes particularly noteworthy when considering bending-dominated lattices, as the hierarchy can drive their stiffness toward the boundaries, enabling them to outperform their equivalent stretching-dominated rivals.

Hydroclimatic drivers of at‐a‐station hydraulic geometry of Brazilian rivers

The geometry of river channels defines their discharge conveyance capacity and can alter the flood regime. While most rivers follow the Theory of Hydraulic Geometry at-a-station power laws, the spatial patterns of exponents, coefficients, and hydrological controls beyond the scale of river reaches remain unclear. Here, we analyze 290 Brazilian river cross-sections to test the hypothesis that the hydraulic geometry is related to basin hydroclimatic characteristics, with a significant difference between humid and dry basins. We classify the basins draining to each cross-section according to the aridity index and the baseflow index, and analyze the controls on the exponents and coefficients (i.e., parameters) of the at-a-station hydraulic geometry power-laws. Our results show that the exponents and coefficients follow a spatially coherent pattern. The exponent of the width of AGH power law is related to the aridity of the basin, being larger in drier basins with a low baseflow index. The width and velocity coefficients are strongly dependent on the basin area. Whereas the velocity coefficient decreases in large basins, the width coefficient increases in large basins, and the spatial distribution of width exponent is related to the bankfull cross-section shape. The combined analysis of hydraulic geometry and basin characteristics is a promising tool for discharge estimation in ungauged basins, flood management, and maintenance of natural rivers.

A scale-span method to characterize the mechanical property of BCF/PEEK considering uncertain structural characteristics

The focus of this study is exploring a scale-span characterization method to predict the mechanical properties of Braided Carbon Fiber Reinforced Poly Ether Ether Ketone (BCF/PEEK) considering structural uncertainty. Firstly, a complicated micro-scale Representative Volume Element (RVE) model that considers the random position and size of fiber was established via the developed Python script. Analogously, a mathematical expression adopted by the trust region algorithm was proposed to accurately describe the detailed cross-sectional shapes and fluctuation amplitude characteristics of BCF/PEEK for the sake of establishing the precision meso-scale RVE model. Then, the corresponding elastic properties that consider fiber volume fraction and fiber distribution location were characterized via the span-scale characterization method. Meanwhile, the influence of fiber bundle fluctuation amplitude and fiber volume fraction on the mechanical properties was investigated as well. In addition, the mechanical properties of BCF/PEEK with the change of the braid angle between warp and weft yarn were predicted via the established meso-scale RVE model. Finally, a series of experiments have been carried out. The maximum and minimum absolute prediction deviation of all elastic property parameters were only 4.07 % and 1.41 %, respectively, which verified the proposed scale-span characterization method can predict the mechanical properties of composites well.

A global springback compensation method for manufacturing metallic seal ring with complex cross-section and submillimeter precision

The fabrication of complex thin-walled components with irregular cross-sectional geometries often necessitates multi-pass forming processes. The springback phenomena at the microscale level contribute significantly difficulty to the precise control of geometrical accuracy for such components. To achieve submillimeter precision control of micro features in metal seal rings, this research proposed a global springback compensation method to facilitate the attainment of the optimized surfaces of dies. Through the analysis of changes in cross-sectional shape, stress distribution and bending moment in the multiple stages, several partition points were set up to divide the cross-section into four zones. For a partitional control of the manufactured surface, the compensation magnitudes for each segment are determined by iteratively refining the compensation factors using the secant method. The iteration of compensation factors is based on the deviation of dimensions measured by finite element simulation, which greatly saves experimental costs. The experimental results indicate that the predictive dimensional alterations by the global compensation agree with the experimental ones exhibiting a maximum error of less than 3 %. Furthermore, the springback behavior during the unloading and trimming stages coupling caused a dimensional error of 14.9 % for the wave width and 8.3 % for the peak width. Following the application of coupled compensation through two iterations, a distinct decrease in the relative average errors of springback values for both part width and peak width, achieving reductions to 2.4 % and 0.6 %, respectively. Compared to the traditional single springback compensation technique, the global compensation strategy effectively mitigates the out-of-tolerance issues induced by the trimming process.

The impact of mechanical stress on anatomy, morphology, and gene expression in Urtica dioica L.

Main conclusionMechanical stress induces distinct anatomical, molecular, and morphological changes in Urtica dioica, affecting trichome development, gene expression, and leaf morphology under controlled conditionsThe experiments were performed on common nettle, a widely known plant characterized by high variability of leaf morphology and responsiveness to mechanical touch. A specially constructed experimental device was used to study the impact of mechanical stress on Urtica dioica plants under strictly controlled parameters of the mechanical stimulus (touching) and environment in the growth chamber. The general anatomical structure of the plants that were touched was similar to that of control plants, but the shape of the internodes' cross section was different. Stress-treated plants showed a distinct four-ribbed structure. However, as the internodes progressed, the shape gradually approached a rectangular form. The epidermis of control plants included stinging, glandular and simple setulose trichomes, but plants that were touched had no stinging trichomes, and setulose trichomes accumulated more callose. Cell wall lignification occurred in the older internodes of the control plants compared to stress-treated ones. Gene analysis revealed upregulation of the expression of the UdTCH1 gene in touched plants compared to control plants. Conversely, the expression of UdERF4 and UdTCH4 was downregulated in stressed plants. These data indicate that the nettle's response to mechanical stress reaches the level of regulatory networks of gene expression. Image analysis revealed reduced leaf area, increased asymmetry and altered contours in touched leaves, especially in advanced growth stages, compared to control plants. Our results indicate that mechanical stress triggers various anatomical, molecular, and morphological changes in nettle; however, further interdisciplinary research is needed to better understand the underlying physiological mechanisms.

Enhancing compressive behavior of concrete with novel low-cost hybrid passive confinement including large rupture strain cotton ropes: Experimental findings and a design-oriented model

Recent research have highlighted the potential of hybrid confinement, combining high tensile strength fiber-reinforced polymers with large rupture strain confinement. This study presents experimental findings on 64 cylindrical and square-shaped specimens tested under axial compression, introducing a novel hybrid confinement method utilizing low-cost fiberglass chopped strand mat sheets and cotton ropes (COFS confinement). The experimental and analytical results yielded several key conclusions. Firstly, circular specimens exhibited significant peak strength increases in various subgroups, with enhancements ranging from 97.5 % to 285.5 %, and ultimate strain improvements ranging from 588.6 % to 1650.0 %. Similarly, square specimens under COFS confinement also demonstrated notable enhancements in ultimate strength and strain, with increases up to 244.7 % and 1083.0 %, respectively, particularly evident with higher levels of confinement. The influence of cross-sectional shape on compressive strength, strain, and energy dissipation was noted, with COFS confinement notably improving these factors for circular sections. Additionally, the study found that as the unconfined compressive strength increased, the enhancement in compressive strength, ultimate strain, and energy dissipation decreased. Moreover, the confinement ratio positively affected axial behavior improvement, with a proportional enhancement observed. However, the efficacy of the confinement ratio was influenced by cross-section type and plain concrete strength, emphasizing the need for considering these factors in COFS-based confinement design. Lastly, an analytical design-oriented model proposed for approximating stress vs. strain curves of COFS-confined concrete showed close agreement with experimental results, providing valuable insights for future design considerations.

Numerical Investigation on Thermal Conductivity of Graphene Foam Composite for Thermal Management Applications.

Graphene foam prepared by the chemical vapor deposition method is a promising thermal interfacial material. However, the thermal properties of graphene foam highly depend on the experimental fabrication conditions during the chemical vapor deposition process. Aiming to reveal how to prepare the appropriate graphene foam for the various thermal management scenarios, the influence of experimental conditions on thermal properties of graphene foam was investigated. Furthermore, the contribution of thermal conductivity and thermal radiation to the effective thermal coefficient of graphene foam was carried out for comparison. The research results showed that the porosity and the cross-section shape of the struts of the growth template were two critical factors affecting the thermal transport of graphene foam, especially with the increase of temperature. In addition, the deposition time of graphene determined the wall thickness and affected the thermal conductivity directly. The thermal radiation contributed more than thermal conductivity when the temperature climbed continuously. Comparatively, the effective thermal coefficient of graphene foam composite with high porosity and circular-shape struts was much superior to that of others at high temperature. The research findings provide important guidance for graphene foam fabrication and its applications in the field of thermal management.

Method of Average Vertical Earth Pressure for HFCCTs Based on Differential Settlement

AbstractThis paper presents a modified and simplified calculation method, taking into account the differential settlement between the soil columns surrounding the cut-and-cover. High-filled cut-and-cover tunnels (HFCCT) are usually subjected to high earth pressures above the top of the CCT due to an ultra-high backfill. However, the estimation methods for earth pressure above the top of CCT are ambiguous. Through the theoretical analysis of the average vertical earth pressure (AEP) at the top of the CCT, it is found that an additional earth pressure above the top of the overburden pressure is induced, and the magnitude is related to the differential settlement between interior and exterior soil columns. Thus, through a combined theoretical derivation and numerical analysis, a modified formula is proposed. The results show that the vertical earth pressure increment above the top of CCT can be linearly correlated to the differential settlement. In addition, the correlation needs to be calibrated by considering several effects on sites, such as slope angle, groove-width ratios, cross-sectional shape, and the type of backfill. The change in influencing factors has no effect on the function type of the p−δ fitting curve, but it will affect the coefficient k.

The Effect of Basic Building Materials and Their Paving Shapes on the Thermal Performance of Walls in Iraqi Residential Buildings

ABSTRACT Iraq's high climatic temperature affects buildings' thermal performance, leading to increased electrical energy consumption due to population growth. Researchers are exploring methods to reduce this consumption, such as heat gain reduction, heat transfer prevention, thermal insulators, high-thermal resistance materials, positive building design, useful orientation, and clean energies. The study investigates solar heat transfer in Iraqi air-conditioned spaces using nine models to analyze the impact of building elements on residential walls and their cross-section shape. The aim is to determine the best model for the Iraqi climate and the optimal approach for achieving optimal solar heat transfer. The study reveals that Model A has negative thermal performance, while Model C and I offer superior thermal performance. Model C offers 47.34% energy savings and Model I 43.99%, aligning with the global trend for green buildings and low energy expenditure in Iraqi residential units.

A high-throughput flowless microfluidic single and multi-solute concentration gradient generator: Design and parametric study.

Microfluidic concentration gradient generators (μ-CGGs) are critical in various biochemical assays, including cell migration, drug screening, and antimicrobial susceptibility testing. However, current μ-CGGs rely on integration with flow systems, limiting their scalability and widespread adoption owing to limited infrastructure and technical expertise. Hence, there is a need for flowless diffusional gradient generators capable of standalone operation, thereby improving throughput and usability. In this study, we model such a diffusional μ-CGG as an infinite source-sink system to capture two characteristic timescales: (i) gradient generation dictated by the diffusion timescale and (ii) stability determined by the rate of change in reservoir concentrations. Through finite-element simulations, we explored the influence of various geometric parameters such as the channel length, cross-sectional area, node and reservoir volumes, and the solute diffusivity on these timescales, along with experimental confirmation using fluorescent tracer diffusion. Our results show that while the gradient stability strongly depends on the reservoir volumes, diffusion length, and solute diffusion coefficient, they are independent of the node shape or the shape of the channel cross section. However, gradient profiles were found to be the strong functions of the diffusion length, solute diffusivity, and the geometric pattern of the microfluidic grid. Additionally, we showcased the versatility of the design by generating discrete gradient profiles and combinatorial gradients of two and three solutes, thus improving throughput in a wide range of on-chip biological assays. These findings underscore the potential of our microfluidic device as an easy-to-use, inexpensive, efficient, and high-throughput platform for various on-chip biological assays.

Effective Stiffness and Damping Analysis of Steel Damper to Lateral Cyclic Loading

Steel dampers are components used in building structures to reduce vibration and energy generated by dynamic loads such as earthquakes. Several factors affect the effectiveness of steel dampers in reducing energy, including the cross-sectional area, mass distribution, cross-sectional geometry, and material stiffness. The cross-sectional geometry or shape of the steel damper can affect how energy is absorbed and dissipated in the structural system. Cross sections with different geometric variations can have different mechanical responses to dynamic loads. This study aims to analyze which type of steel damper is effective in terms of stiffness and damping capacity against lateral cyclic loads. The steel damper cross-sectional variations used are slit steel dampers (SSDs), tapered steel dampers (TSDs), and oval steel dampers (OSDs). Cyclic testing of the dampers used displacement control with the same target deviation for all three damper types. The results showed that the stress and strain distributions of the oval steel damper were more even than those of the other two models. The variations in the energy dissipation capacities of the three cross-section variations are relatively the same. However, the slit steel damper type has the best stiffness compared to the other two types. This research is ultimately expected to influence the science of the structure of a building in preventing and anticipating earthquakes or other disasters. Doi: 10.28991/CEJ-2024-010-07-017 Full Text: PDF

Nonlinear gyrokinetic modelling of high confinement negative triangularity plasmas

Nonlinear gyrokinetic simulations correctly predict particle as well as ion and electron energy fluxes of high confinement plasmas with a negative triangularity cross sectional shape, showing that core transport in these plasmas is well described by standard gyrokinetic models. Experimentally inferred power balance fluxes are mostly reproduced within one standard deviation across a wide portion of the minor radius. Experimental conditions are reproduced by ion scale simulations, without the need to include density and temperature profile curvature effects. The experimental case is used as baseline to predict that the non-dimensional confinement scaling in negative triangularity plasmas increases strongly with plasma current while slightly degrading at increasing normalized pressure and decreasing collisionality. Recent experiments showed that low toroidal rotation negatively impacts confinement; consistent with the experiment, simulations predict that low rotational shear significantly affects confinement unless the plasma effective charge is maintained above a minimum level. Core confinement is predicted to significantly degrade in low aspect ratio devices.

Cross-section design of the flow channels in membrane electrode assembly electrolyzer for CO2 reduction reaction through numerical simulations

Membrane electrode assembly (MEA) is widely considered to be the most promising type of electrolyzer for the practical application of electrochemical CO2 reduction reaction (CO2RR). In MEAs, a square-shaped cross-section in the flow channel is normally adopted, the configuration optimization of which could potentially enhance the performance of the electrolyzer. This paper describes the numerical simulation study on the impact of the flow-channel cross-section shapes in the MEA electrolyzer for CO2RR. The results show that wide flow channels with low heights are beneficial to the CO2RR by providing a uniform flow field of CO2, especially at high current densities. Moreover, the larger the electrolytic cell, the more significant the effect is. This study provides a theoretical basis for the design of high-performance MEA electrolyzers for CO2RR.

SELECTION OF THE OPTIMAL MACHINERY COMPLEX FOR CONSTRUCTING IRRIGATION CANALS WITH A PARABOLIC PROFILE

An analysis of the experience of dredger operation in various industries allows us to identify the following main problems that need to be addressed to improve their efficiency: improvement of papillonation schemes and structural enhancement of the main equipment from a hydraulic perspective. The current soil intake devices, suction lines, and soil pumps do not always fully meet the specific requirements of soil development conditions. The objectives of the present research were to propose ways to enhance the performance of systems for automatic control of dredger work movements and automatic regulation of the soil intake process. These proposals aim to create a parabolic cross-sectional shape of the canal during development, ensure the highest productivity and lowest energy consumption, as well as low work costs, using modern control devices. The effect of the proposed technology for canal development using dredgers with automated papillonation consists of the following: providing the developed canals with a stable cross-sectional shape; automating the papillonation of the dredger and optimizing the operation of the soil pump; Implementing shift-based production accounting; using soil meters in the automated system. Giving the developed canal a cross-sectional shape that is stable in both hydraulic and static aspects has allowed for the following benefits: increased sediment transport capacity of the flow, while simultaneously reducing the cross-sectional area, growth of vegetation, water level fluctuations, water losses, and the right-of-way strip; reduced the volume of cleaning work by up to 20%; increased the period between cleanings by ensuring uniform flow movement; enhanced the productivity of dredgers by concentrating sediment on the canal slopes without changing the overall volume of cleaning.

COMPARATIVE ANALYSIS OF THE EFFICIENCY OF PARABOLIC AND TRAPEZOIDAL SECTIONS IN IRRIGATIONCANALS

One of the current scientific directions in hydraulic engineering is to give irrigation canals a hydraulically and statically stable cross-sectional shape in the form of the most advantageous parabolic profile. This approach allows maximizing the sediment transport capacity of the flow and significantly reducing the time and costs of construction and maintenance works, using optimization criteria for next-generation machinery and mechanisms. The significance of this research lies in developing a new concept for designing, constructing, and operating irrigation canals in hydraulic engineering systems with cross-sectional shapes that are both hydraulically and statically stable. These shapes aim to maximize sediment transport capacity, ensure ecological sustainability of natural-technical basin systems, and contribute to national food security. The objects of study are hydraulic engineering structures, specifically the inter-farm canals of irrigation systems within the Syr Darya river basin in the southern region of the Republic of Kazakhstan. For the study, methods were used including stability analysis of earth slopes using circular-cylindrical sliding surfaces, methods based on analogy between shear curves and slopes, and methods based on the theory of limit equilibrium. Calculations have demonstrated the advantages, including increased resistance to cross-section deformation, reduced earthwork volumes during irrigation canal construction and cleaning by 20-25%, decreased materials and work volume for possible lining by 13-18%, narrower canal top width and land acquisition zones by 11-17%, lower labor costs by 13-16%, reduced construction costs by 14-18%, and decreased specific adjusted costs by 15-18%.

Energy Absorption and Failure Modes of Different Composite Open-Section Crush Elements under Axial Crushing Loading.

In order to study the energy absorption characteristics of the open-section thin-walled composite structures with different cross-sections, axial compression tests were carried out at loading speeds of 0.01 m/s, 0.1 m/s, and 1 m/s. Finite element models were built to predict the crushing response and energy absorption behaviors of these open-section structures. The effects of the cross-section's shape, cross-section aspect ratio, trigger mechanism, and loading speed on the energy absorption characteristics of the composite structures were analyzed. The results show that the average crushing loads of the hat-shaped and Ω-shaped open-section structures are 14.1% and 14.6% higher than those of C-shaped open-section structures, and the specific energy absorption (SEA) values are 14.3% and 14.8% higher than that of C-shaped open-section structures, respectively. For the C-shaped open-section structures, a 45° chamfer trigger is more effective in reducing the initial peak load, while a 15° steeple trigger is more appropriate for the hat-shaped open-section structures. The average crushing loads and SEA of C-shaped, hat-shaped, and Ω-shaped open-section structures are reduced when the loading speed is increased from 0.01 m/s to 1 m/s. The increase in loading speed leads to the splashing of debris and thus reduces the loading area and material utilization of open-section structures, leading to a decrease in energy absorption efficiency.

Blast wave interaction during explosive detonation in a variable cross-sectional charge

Purpose. The research aims to assess the efficiency and performance of solid media destruction in directed blasting of a charge with variable cross-sectional shape. Methods. Numerical modelling of the blast wave interaction process is performed using the finite element method based on the Euler-Lagrange algorithm. The Johns-Wilkins-Lee equation of state is used to determine the pressure-volume dependences of medium destruction. Assessment of solid medium destruction mechanism during a directed blasting of a charge with variable cross-sectional shape is carried out based on polarization-optical method on models made of optically active material. Findings. Experimental studies of solid medium destruction by the action of directed blasting with a variable cross-section charge made it possible to determine the direction of blast wave propagation and its amplitude in stress wave, influencing the intensity of radial crack network formation in superposition areas, and directed perpendicularly to explosive cavity. At the same time, the average peak pressure in collision zone of two shock waves in centre of spherical cavity is approximately 1.48 and 1.84 times higher than that in weakly blast-loaded areas. It has been found that when two shock waves collide and superimpose on each other, the intensity of their impact increases. Moreover, the shock wave velocity in collision zone is higher than that of the radial shock wave. Originality. It has been determined that the maximum pressure values on the explosive cavity wall at the initiation points sharply increase and then gradually stabilize as the blast stress waves propagate and have an arbitrary distribution pattern. Three areas should be considered: not superimposed, weakly superimposed, and strongly superimposed. At each point of detonation, the pressure on explosive cavity wall will be minimal, while in the charge centre in the spherical insert zone, on the contrary, it will be maximal. In this case, the pressure in the central superposition area is about 2.84 times greater than at the initiation ends, and the nature of distribution changes according to a linear dependence. Practical implications. The performed research findings can serve as a basis for development of effective parameters of resource-saving methods for stripping hard rocks of complex structure in the conditions of ore mines.

Optimization Design Method for Vibration Reduction of Frame Structure of Cable-Driven Parallel Robot

This paper proposes a comprehensive optimization algorithm for the crossbeam cross-section size to solve the vibration problem of the flexible cable-driven parallel robot frame. The goal is to achieve an innovative design of the cross-sectional structure. By using a differential evolution algorithm, a comprehensive scale analysis of the cross-section size of the beam is carried out. This optimization method effectively improves the cross-section moment of inertia and the bending stiffness of the beam. Additionally, based on the variable density penalty method, the topological optimization design of the cross-section is carried out under the condition of minimum flexibility, the optimization objective function is established, and the objective function is solved by the moving asymptote method. The optimization results show that the beam stiffness is maximized while meeting the minimum flexibility required by the project. Through comparative analysis with various aluminum profile structures and their constructed frames, it is verified that the cross-sectional shape obtained through the optimized design method can significantly improve the anti-vibration stability of the frame.

Analysis of Vibration Performance by Height of Column-type Jig for Vibration Test with Cross-sectional Shape Based on Optimization

Analysis of Vibration Performance by Height of Column-type Jig for Vibration Test with Cross-sectional Shape Based on Optimization

Analysis of the Drag-Reduction Ability of the Layout and Cross-Sectional Shapes of Subsea Structures in the Critical Flow Mode

Introduction. Slender structures of subsea energy production systems are under constant influence of currents and waves. Hydrodynamic loads result from the interaction of subsea pipelines, umbilicals, equipment supports with fluid flows, and lead to the vortex formation in the area behind the structures. Vortex-induced forces are the sources of the cyclic loading. They accelerate gradually the fatigue damage, which may result in a failure. One of the ways to reduce the loads on subsea structures is to alter the shape of a cross-section, taking into account the flow regime. Dependence of the resulting hydrodynamic loads on the cross-sectional shape and relative position of structures has not been studied in details for the uniform flow in the critical mode. The current work is aimed at filling this gap. The research objective is to consider the impact of the distance between the structures, and also, the presence of a D-shaped structure, placed upstream relative to the group of three cylinders of different cross-sectional shapes.Materials and Methods. The computational fluid dynamics approach was used in this work for numerical simulations of vortex-induced forces in the ANSYS Fluent software for cylinder with D = 0.3 m. Modelling was conducted with the Detached Eddy Simulation (DES) method, which combined advantages of the Reynolds-averaged Navier-Stokes equation (RANS) method and the Large Eddy Simulation (LES) method. The object of the research was the system of four structures in the 2D computational domain, which included the upstream D-shaped cylinder and the main group of three cylinders with the circular, squared and diamond shapes of the cross-section. The transient process was considered, where structures were under the influence of the uniform flow in the critical regime at Re = 2.5×10⁵.Results. Five sets of data were obtained in simulations for the time-dependent coefficients of the lift and drag forces: for the main system — of the D-shaped, circular, square and diamond structures, and also for the four systems — of only D-shaped, only circular, only square and only diamond shaped structures. Additional analysis was conducted for the effect of the distance between the structures on the amplitude of fluctuating hydrodynamic force coefficients. The obtained results are presented as time histories of coefficients of the lift and drag forces, frequency analysis and contours of velocity, pressure and vorticity fields. The results indicate a positive effect of the upstream D-shaped structure on reducing the drag force, acting on the central structure in the group of three cylinders located downstream.Discussion and Conclusion. The results of the performed studies facilitate the informed decisions regarding the arrangement of subsea structures in a group of four objects, depending on the cross-sectional shape and the distance between the structures. The upstream D-shaped structure provides reducing the hydrodynamic drag force acting on the central structure in the downstream group of three structures, thereby slowing the fatigue accumulation and increasing the time of safe operation.