Flow Boundary Research Articles

Large Eddy Simulation of Flow Around Twin Tower Buildings in Tandem Arrangements with Upstream Corner Modification

The aerodynamic performance of twin tall buildings immersed in the atmospheric boundary layer was numerically investigated by adopting the spatial-averaged large eddy simulation (LES) method. This study focused on the effects of corner cutting and chamfering. The buildings were both square and sectional with a width-to-height ratio of 1:6, and were arranged in a tandem configuration with a spacing ratio of 2.0. The corner-cutting and chamfering measures were only applied to the upstream cylinder, with a corner modification rate of 10%. To generate the turbulent inflow boundary condition (IBC) for LES, steady-state equilibrium IBC expressions were introduced into the vortex method, which were implemented in the commercial code Ansys Fluent. The present simulation method and solution parameters were first verified by comparing the simulated wind field and the wind pressure distribution on a single tall building with those of the wind tunnel test. The influences of the corner-cutting and chamfering measures on the wind load of the tandem buildings were then comparatively studied concerning the statistical values of their aerodynamic force coefficients and wind pressure coefficients. The influence mechanism was analyzed based on the simulated time-averaged flow field and the instantaneous vortex structure around the buildings. The results indicated that upstream corner-cutting and chamfering measures can induce a diffusion angle shift in the separated shear flow from the leading edge of the upstream building, thus affecting the separation and reattachment of the separated upstream flow on the downstream building. Among the measures studied, upstream corner cutting is more effective in reducing wind pressure and aerodynamic force coefficients.

Numerical simulation of YSO jet collimated by toroidal magnetic fields and radiative cooling effect

Abstract The mechanism of generation and collimation of young stellar object jets remains an unsolved problem and is a research hotspot in contemporary astrophysics. Here, we conducted a two-dimensional cylindrical coordinates simulation experiment using radiative magnetic-hydro-dynamic FLASH code and systematically analyzed the effects of toroidal magnetic fields generated by Biermann battery term and radiative cooling effect on jet evolution. In the simulation, strong toroidal magnetic fields are generated at the boundary of the plasma flow. A comparison of jets generated in different cases indicates that the magnetic fields play a significant role in hydrocarbon (CH) plasma jet collimation, surpassing the impact of radiative cooling effects. Additionally, it is observed that the magnetic fields can alter knots velocities. This platform provides a way to investigate the role of toroidal magnetic fields in jet evolution without external devices and provides a better understanding of the evolution of protostellar jets.

A mathematical model for the interaction of anisotropic turbulence with porous surfaces

Leading-edge noise is a complex phenomenon that occurs when a turbulent fluid encounters a solid object, and is a notable concern in various engineering applications. This study enhances a mathematical leading-edge noise model (Hales et al., J. Fluid Mech., vol. 970, 2023, A29) for anisotropic flow and porous boundaries. The model has two key components. First, we adjust the velocity spectrum to account for the possibility of anisotropy in the flow. This paper rigorously introduces a third dimension for the turbulence spectrum that preserves the turbulence kinetic energy and mathematical definitions for integral length scales. Second, we adapt the fully analytical acoustic transfer function to account for different boundaries by implementing convective impedance boundary conditions when formulating the gust-diffraction problem. This problem is then solved using the Wiener–Hopf technique. We discuss important aspects of this method, including the factorisation of a non-trivial scalar kernel function and the application of suitable edge conditions for the problem. Each modification is inspired by experimental leading-edge noise data using a series of different porous leading edges and anisotropic turbulence generated by a cylinder upstream of the edge. Experimental data demonstrate the interplay between anisotropy and leading-edge modifications while achieving the characteristic mid-frequency noise reduction expected from porous leading edges. Our model is adapted to best fit the trends of the data via a tailored impedance function, leading to good agreement with all datasets across an extended frequency range. This tailored function is used to successfully validate the model against other datasets from a different set of experiments.

Enhancing prediction of separation point location in thrust-optimized contoured nozzles with new realizability constants in the k-ω turbulence model

The objective of this study was to examine the capability of the realizable k–ω turbulence model to accurately predict the position of the separation point in hypersonic flows. While the two-equation k–ω model is suitable for predicting boundary flows with zero pressure gradients, its reliability decreases for flows with adverse pressure gradients, particularly in complex flows where normal stresses calculated using the Boussinesq approximation can become negative and “non-realizable” under high strain conditions. To address this problem, this study proposes a solution by introducing new variables in the Cμ formulation of the realizable model, which can limit eddy viscosity and enhance its sensitivity to the mean flow and turbulence models. We conducted numerical simulations and found that the realizable model produced improved results that were close to those of the experimental data. These findings highlight the potential of the new constants of the realizable k–ω turbulence model to accurately predict the location of compressible turbulent separation points in hypersonic flows.

Estimation of wind energy potential through experimental investigation of boundary layer in small wind tunnel

In Brazil, the persistent increase in electricity consumption, primarily propelled by economic and technological advancements, can exceed the capacity of generation and distribution, underscoring the imperative for alternative energy sources. Given the compromised state of hydroelectric power and the environmental ramifications of thermoelectric plants, wind energy emerges as a promising and sustainable solution. Research in this domain encompasses turbine efficiency and analysis of local wind potential. Precise determination of this potential is pivotal to ensure project viability and efficacy, directly impacting decisions of electrical generation companies. Tests for assessing wind potential can be conducted in situ or employing techniques such as Fluid Dynamics, crucial for large-scale projects. Experimental investigations, particularly those conducted in wind tunnels, assume a foundational role in research and development in this field. The distribution of wind velocity across the test section stands as a critical parameter, with accurate simulation of the atmospheric boundary layer being indispensable for dependable outcomes. The boundary layer, an area adjacent to the surface influenced by friction between solid and fluid, holds a crucial role in drag and heat transfer. Various techniques have been devised to simulate and control the boundary layer in wind tunnels, representing a burgeoning area of inquiry. The present study advocates for the utilization of the 'boundary layer plate with flap device' to examine how different flap angles and Reynolds numbers impact boundary layer height, employing experimental design with factorial planning for result analysis. Subsequently, the obtained results indicate that flap angle significantly alters the boundary layer height within a given range of Reynolds numbers, thereby enabling the simulation of diverse boundary layer heights within a small wind tunnel, facilitating experiments related to wind flow and atmospheric boundary layer. Consequently, this research contributes to the estimation of wind potential and propels the efficient utilization of wind energy as a clean and renewable source.

Super-resolution reconstruction of wind fields with a swin-transformer-based deep learning framework

Deep learning approaches that allow for the rapid simulation of high-resolution atmospheric turbulence are expected by using the super-resolution (SR) technique. Recently, the shifted window attention mechanism in Swin-Transformer offers a significant improvement compared with the vanilla attention mechanism. This method restricts the attention computation to a local neighborhood, reducing the computational load to a linear relationship with sequence length. However, its original architecture is unsuitable for the SR in turbulence due to the mismatch with classification, detection, and segmentation tasks. In this study, the hierarchical structure is redesigned, and a new relative position representing approach is introduced to facilitate the SR procedures of turbulent wind. The channel-shuffled perceptual loss is integrated into the loss function to guide the update of weight parameters. The experimental cases of idealized two-dimensional turbulent flow and realistic boundary layer wind are employed to validate the performance. The results suggest that the proposed approach remarkably outperformed the previous Super-Resolution Convolutional Neural Network, Deep Statistical Downscaling, and Regional Climate Model Emulator in wind vectors. It exhibits lower values than the other three networks whether in terms of point-wise metrics like mean square error, mean absolute error, mean absolute percentage error, or perceptual metrics, including structural similarity index measure and probability density functions. The reconstructed wind vectors closely match the target high-resolution results. This study will help advance the application of shifted window attention mechanisms in wind field SR.

Deep Circulation Variability through the Eastern Subpolar North Atlantic

Abstract The export of the North Atlantic Deep Water (NADW) from the subpolar North Atlantic is known to affect the variability in the lower limb of the Atlantic meridional overturning circulation (AMOC). However, the respective impact from the transport in the upper NADW (UNADW) and lower NADW (LNADW) layers, and from the various transport branches through the boundary and interior flows, on the subpolar overturning variability remains elusive. To address this, the spatiotemporal characteristics of the circulation of NADW throughout the eastern subpolar basins are examined, mainly based on the 2014–20 observations from the transatlantic Overturning in the Subpolar North Atlantic Program (OSNAP) array. It reveals that the time-mean transport within the overturning’s lower limb across the eastern subpolar gyre [−13.0 ± 0.5 Sv (1 Sv ≡ 106 m3 s−1)] mostly occurs in the LNADW layer (−9.4 Sv or 72% of the mean), while the lower limb variability is mainly concentrated in the UNADW layer (57% of the total variance). This analysis further demonstrates a dominant role in the lower limb variability by coherent intraseasonal changes across the region that result from a basinwide barotropic response to changing wind fields. By comparison, there is just a weak seasonal cycle in the flows along the western boundary of the basins, in response to the surface buoyancy-induced water mass transformation.

Energy conversions at shock wave interaction with pulse discharge in profiled channel

The objective of this paper is to conduct a comprehensive investigation of the thermal and gas dynamic flow fields generated during the interaction of pulsed volume discharge plasma with high-speed channel flow. A comparative visualization was carried out using high-speed infrared thermography and shadowgraphy techniques. We examined phenomena related to both plasma and gas dynamic interactions within a special test section of the gas dynamic channel. The spatial–temporal characteristics of the thermal fields associated with these plasma and gas dynamic interactions were analyzed, together with infrared radiation intensity diagrams. The dynamics of discontinuities and inhomogeneities resulting from the interaction of shock waves with the pulsed volume discharge plasma—referred to as discontinuity breakdown—were also investigated. We compared two physical mechanisms of energy conversion into infrared radiation recorded by the thermal imager in the range of 1.5–5.1 μm. These mechanisms include low-temperature plasma emission from a sub-microsecond localized volume discharge and the sub-millisecond radiation from the inner surfaces of glass walls heated due to thermal conductivity at the interface with the gas flow boundary layer.

Numerical study on vibration heat transfer enhancement of multi-configured blunt-headed cylinder with fin device

The large-scale flow-induced deformation is an effective heat transfer enhancement technology. Then, a blunt-headed cylinder with fin (BHC-F) was proposed to evaluate the heat transfer enhancement performance using flow-induced vibration with different configuration (incident angle Φ). The two-way fluid structure interaction method was utilized to explore the vibration response, flow field and heat transfer performance of BHC-F at Reynolds numbers Re = 500–1500. Vibration results found that the vibration displacement of BHC-F increased with the increase of Φ (0°–180°), which leaded to the acceleration of flow boundary layer separation. When Φ = 180°, the peak displacement of BHC-F reached 3.12 mm, which was 61.66 % and 34.48 % higher than that of Φ = 0° and 90°, respectively. At this time, heat transfer enhancement was obtained because the thermal boundary layer was reduced due to the interaction between the vortex and the wall. In addition, the PEC under all configurations were all greater than 1, indicating that BHC-F achieved the purpose of enhanced heat transfer. The increase of Re has a positive effect on the heat transfer enhancement of BHC-F. When Re = 1500, the maximum heat transfer enhancement of BHC-F-90° reached 13.8 %, which was 62.3 and 26.6 times higher than that of BHC-F-0° and BHC-F-180°. This study establishes a theoretical foundation for employing flow-induced vibration in heat transfer enhancement applications and offers technical support for enhancing the overall performance of heat exchangers.

Optimising Physics-Informed Neural Network Solvers for Turbulence Modelling: A Study on Solver Constraints Against a Data-Driven Approach

Physics-informed neural networks (PINNs) have emerged as a promising approach for simulating nonlinear physical systems, particularly in the field of fluid dynamics and turbulence modelling. Traditional turbulence models often rely on simplifying assumptions or closed numerical models, which simplify the flow, leading to inaccurate flow predictions or long solve times. This study examines solver constraints in a PINNs solver, aiming to generate an understanding of an optimal PINNs solver with reduced constraints compared with the numerically closed models used in traditional computational fluid dynamics (CFD). PINNs were implemented in a periodic hill flow case and compared with a simple data-driven approach to neural network modelling to show the limitations of a data-driven model on a small dataset (as is common in engineering design). A standard full equation PINNs model with predicted first-order stress terms was compared against reduced-boundary models and reduced-order models, with different levels of assumptions made about the flow to monitor the effect on the flow field predictions. The results in all cases showed good agreement against direct numerical simulation (DNS) data, with only boundary conditions provided for training as in numerical modelling. The efficacy of reduced-order models was shown using a continuity only model to accurately predict the flow fields within 0.147 and 2.6 percentage errors for streamwise and transverse velocities, respectively, and a modified mixing length model was used to show the effect of poor assumptions on the model, including poor convergence at the flow boundaries, despite a reduced solve time compared with a numerically closed equation set. The results agree with contemporary literature, indicating that physics-informed neural networks are a significant improvement in solve time compared with a data-driven approach, with a novel proposition of numerically derived unclosed equation sets being a good representation of a turbulent system. In conclusion, it is shown that numerically unclosed systems can be efficiently solved using reduced-order equation sets, potentially leading to a reduced compute requirement compared with traditional solver methods.

Development of a methodology and design of a device for determining the Mach number of a supersonic flow

The paper presents the developed methodology and designed a device for determining the Mach number during supersonic gas outflow. An analysis of various methods for determining the Mach number was carried out, including measuring the pressure at the flow boundary, the use of shock waves, and the use of optical methods. A comparison was made of the accuracy of the readings when using the considered methods. Based on the results obtained, a technique for high-precision determination of the Mach number has been developed, including a combination of several independent measurement methods. A device has been designed that implements this measurement technique, and the results of experimental tests in a wind tunnel have been reviewed, including instrument readings, graphs and tables confirming the accuracy and reliability of the data obtained. Their accuracy and reliability are analyzed. Using the analysis, it is possible to ensure the selection of the most rational method for determining the Mach number at the initial stage of designing aircraft, such as airplanes, missiles, fighters, and UAVs. Accurate knowledge of the Mach number allows engineers to optimize the aerodynamic characteristics of the aircraft, ensure flight safety, improve engine efficiency and overall air transport performance. In addition, the Mach number is the most important criterion of similarity when modeling in aerodynamic research, which makes the developed methodology and device relevant not only for the design of aircraft, but also for a wide range of scientific and engineering research in the field of aeronautical technology. It is emphasized that the presence of a reliable method for determining the Mach number can significantly reduce the time and resources spent on testing and improving aircraft, and also contributes to the development of innovative technologies in the field of aviation and astronautics.

Patient-specific, multiscale modelling of neointimal hyperplasia in lower-limb vein grafts using readily available clinical data

The prediction of neointimal hyperplasia (NIH) growth, leading to vein graft failure in lower-limb peripheral arterial disease (PAD), is hindered by the multifactorial and multiscale mechanobiological mechanisms underlying the vascular remodelling process. Multiscale in silico models, linking patients’ hemodynamics to NIH pathobiological mechanisms, can serve as a clinical support tool to monitor disease progression. Here, we propose a new computational pipeline for simulating NIH growth, carefully balancing model complexity/inclusion of mechanisms and readily available clinical data, and we use it to predict NIH growth for an entire vein graft. To this end, three different fittings to published in vitro data of time-averaged wall shear stress (TAWSS) vs nitric oxide (NO) production were tested for predicting long-term graft response (10-month follow-up) on a single patient. Additionally, the sensitivity of the model’s predictions to different inflow boundary conditions (BCs) was assessed. The main findings indicate that: (i) a TAWSS-NO hyperbolic relationship best predicts long-term graft response; (ii) the model is insensitive to the inflow BCs if the waveform shape and the systolic acceleration time are comparable with the one acquired at the same time as the computed-tomography scan. This proof-of-concept study demonstrates the potential of using multiscale, computational techniques to predict NIH growth in lower-limb vein grafts, considering the routine clinical scenario of non-standardised data collection and sparse, incomplete datasets.

Well-Test Interpretation Model of Water-Injection Well in a Low-Permeability Reservoir and Its Application

For low-permeability reservoirs, water-flooding development is usually adopted, which leads to induced fractures near the wellbore, increasing reservoir heterogeneity, and making water-flooding development more complex. This paper focuses on low-permeability reservoirs, considering the characteristics of induced fractures and elliptic-flow composite, and the well-test model for injection wells is established. The mathematical model in Laplace space is obtained through dimensionless transformation and Laplace transformation. Subsequently, the Mathieu function is introduced to obtain the bottom hole pressure, and the pressure response curve is drawn. The six flow stages of the curve are defined, and the sensitivity of parameters such as half-length of induced fractures, range of lateral-swept area, permeability in unswept area, and outer boundary distance at constant pressure are analyzed. The results show that the half-length of the fracture mainly affects the linear flow of the fracture, the range of the lateral wave-affected area mainly affects the radial flow of the swept area, the permeability of the unswept area mainly affects the radial flow of the unswept area, and the outer boundary distance at constant pressure mainly affects the boundary flow. Based on the production performance of a certain injection well in J Oilfield, a series of key parameters are obtained through analytical solution model inversion, including the induced-fracture half-length of 10.32 m, the lateral-swept range of elliptic partition flow of 128.95 m, the permeability of the swept area of 6.87 mD, and the mobility ratio of 119.92, which show the superiority of the analytical solution model.

A displacement formulation for coupled elastoacoustic problems that preserves flow irrotationality

Two-way fluid–structure interaction (FSI) problems, in the sense that a flow induces the motion of a solid, which in turn modifies the flow boundary conditions, have been approached with very different strategies, the most common of which is probably the finite element method (FEM). In the case of elastoacoustics, the flow consists of an acoustic field interacting with a vibrating structure. When the problem is discretized with the FEM, an algebraic block matrix system is obtained and the coupling between the acoustic field and the structure takes place through a coupling matrix with off-diagonal terms. Usually the structure is characterized by its displacement field, while for the acoustics several options are available, ranging from pressure to acoustic displacement or velocity/displacement acoustic potentials. Depending on the formulation, symmetric or asymmetric systems are obtained and different types of numerical stability problems have to be faced. In this work, a monolithic strategy based on the Rayleigh–Ritz method is proposed. The displacement is used as the primary variable for both the structure and the acoustic field and is expanded in terms of Gaussians as basis functions. This provides an algebraic block matrix system for the global uncoupled problem. However, instead of resorting to a coupling matrix, the essential continuity conditions at the acoustic-structure interface are imposed by the nullspace method (NSM). That is, the solution of the uncoupled system is expanded in terms of a basis of the nullspace generated by the essential conditions of the problem, including the displacement continuity constraints at the interface, thus giving the solution of the coupled problem. As for natural conditions, they are imposed in a weak sense. For ease of explanation, a one-dimensional (1D) case is first introduced, followed by the coupling of a 2D acoustic cavity with a beam and a 3D one with a plate. The proposed method is validated with FEM simulations on fine meshes and the advantage of using Gaussian basis functions over trigonometric ones is also demonstrated.

A dynamic linearized wall model for turbulent flow simulation: Towards grid convergence in wall-modeled simulations

This paper addresses the common issue of (no-)grid convergence in wall-modeled numerical simulations and proposes a dynamic linearization technique applied to the Spalart-Allmaras wall model to achieve a proper behavior on fine grids and low-friction areas. A theoretical analysis of the numerical error committed on the shear stress balance close to the walls is performed. It shows that the error is due to the inappropriate imposition of too steep wall-normal velocity gradients that cannot be properly accounted for on the typical grids used for wall-modeled simulations. Based on this error quantification, a dedicated wall model linearization technique is proposed, following the approach developed by Tamaki, Harada and Imamura in 2017. In the proposed modified linearization method, the linearization distance is modified and adjusted dynamically. This is done according to the theoretical shear stress error estimate, in order to keep the numerical error below a user-defined threshold. The method is applied to well-referenced test cases of increasing complexity from the Turbulence Modeling Resource. Overall, the proposed wall model clearly exhibits appropriate grid convergence properties and is also able to predict accurately non-equilibrium boundary layers and flow separation using proper grid refinement.

The 3D Euler equations with inflow, outflow and vorticity boundary conditions

The 3D incompressible Euler equations in a bounded domain are most often supplemented with impermeable boundary conditions, which constrain the fluid to neither enter nor leave the domain. We establish well-posedness with inflow, outflow of velocity when either the full value of the velocity is specified on inflow, or only the normal component is specified along with the vorticity (and an additional constraint). We derive compatibility conditions to obtain regularity in a Hölder space with prescribed arbitrary index, and allow multiply connected domains. Our results apply as well to impermeable boundaries, establishing higher regularity of solutions in Hölder spaces.

Profiling Phenotypic Heterogeneity of Circulating Tumor Cells through Spatially Resolved Immunocapture on Nanoporous Micropillar Arrays.

The phenotype of circulating tumor cells (CTCs) offers valuable insights into monitoring cancer metastasis and recurrence. While microfluidics presents a promising approach for capturing these rare cells in blood, the phenotypic profiling of CTCs remains technically challenging. Herein, we developed a nanoporous micropillar array chip enabling highly efficient capture and in situ phenotypic analysis of CTCs through enhanced and tunable on-chip immunoaffinity binding. The nanoporous micropillar array addresses the fundamental limits in fluidic mass transfer, surface stagnant flow boundary effect, and interface topographic and multivalent reactions simultaneously within a single device, resulting in a synergistic enhancement of CTC immunocapture efficiency. The CTC capture efficiency increased by approximately 40% for cancer cells with low surface marker expressing. By manipulating fluidic velocity (hydrodynamic drag force) on the chip, a cell adhesion gradient was generated in the capture chamber, enabling individual CTCs with varying expression levels of epithelial cellular adhesion molecules to be immunocaptured at the corresponding spatial locations where equilibrium drag force is provided. The clinical utility of the nanoporous micropillar array was demonstrated by accurately distinguishing early and advanced stages of breast cancer and further longitudinally monitoring treatment response. We envision that the nanoporous micropillar array chip will provide an in situ capture and molecular profiling approach for CTCs and enhance the clinical application of CTC liquid biopsy.

Dynamics of a hot flexible cantilever plate under natural convection heat transfer in a square cavity

This study investigates the fluid-structure interactions of a flapping plate within a square cavity under four distinct boundary conditions, where two opposing walls are heated isothermally, and the others are adiabatic. These configurations are defined as case 1 (cooled side walls), case 2 (cooled top and bottom walls), case 3 (heated bottom and cooled top wall), and case 4 (heated top wall and cooled bottom wall). The effects of non-dimensional parameters, including Rayleigh number (Ra), Cauchy number (Ca), and mass ratio (β) on plate dynamics and convective heat transfer are analyzed. Numerical investigations are executed utilizing the SU2 open-source multi-physics computational fluid dynamics solver, with a fixed Prandtl number (Pr) set at 0.71 and dimensionless temperature difference (ϵ) established at 0.6. The results show that in cases 1 and 4, the plate exhibits no observable unsteadiness, while cases 2 and 3 reveal different oscillatory behavior within certain parameter ranges, including static mode, periodic flapping mode, quasi-periodic flapping mode, and chaotic flapping mode. In particular, the configuration in case 3 possesses higher inherent instability than case 2, causing the earlier onset of Hopf bifurcation. These findings provide valuable insights into the influence of boundary conditions on the behavior of flexible structures in fluid environments, highlighting the critical role of flow instabilities and boundary conditions in determining the dynamic response of the system.

Fast prediction of compressor flow field based on a deep attention symmetrical neural network

Accurate and rapid prediction of compressor performance and key flow characteristics is critical for digital design, digital twin modeling, and virtual–real interaction. However, the traditional methods of obtaining flow field parameters by solving the Navier–Stokes equations are computationally intensive and time-consuming. To establish a digital twin model of the flow field in a transonic three-stage axial compressor, this study proposes a novel data-driven deep attention symmetric neural network for fast reconstruction of the flow field at different blade rows and spanwise positions. The network integrates a vision transformer (ViT) and a symmetric convolutional neural network (SCNN). The ViT extracts geometric features from the blade passages. The SCNN is used for deeper extraction of input features such as boundary conditions and flow coordinates, enabling precise flow field predictions. Results indicate that the trained model can efficiently and accurately reconstruct the internal flow field of the compressor in 0.5 s, capturing phenomena such as flow separation and wake. Compared with traditional numerical simulations, the current model offers significant advantages in computational speed, delivering a three-order magnitude speedup compared to computational fluid dynamics simulations. It shows strong potential for engineering applications and provides robust support for building digital twin models in turbomachinery flow fields.

Calculation of Single and Multiple Low Reynolds Number Free Jets with a Lattice-Boltzmann Method

Numerical calculations of low-Reynolds-number freejets with a Lattice Boltzmann Method are presented. The calculated-time-averaged axial velocity of a round jet with Re=1030 matches experimental data, including the length of transition from laminar to turbulent flow. Special care was needed for the inlet conditions in order to reproduce the vena contracta phenomenon. The results for round jets with Re=1000/1500/2000 show good agreement with Finite Difference Method calculations from the literature. In principle, there is a strong sensitivity to the inlet conditions, suggesting a need in future experimental work to measure in detail the velocity profiles and turbulence quantities at the nozzle outlet. The application of turbulence at the inflow boundary of the calculation domain is often used to emulate sources of disturbances in experiments. The present study demonstrates the need to investigate the impact of turbulence level and length scale at inlet independent of each other. Finally, the calculation for a bundle of nine jets with a square inlet led to the finding that the velocity decay of the central jet is maximal when the spacing between the jets is ca. one jet diameter.