Steady-state Flow Field Research Articles

Influence of Boundary Layer Skew on the Tip Leakage Vortex of an Axial Compressor Stator

Abstract For an axial compressor stator with tip gap, the boundary layer (BL) in the hub endwall region has a significant influence on the development and progression of the tip leakage vortex. Herein, the so-called BL skew, which develops through relative motion of the hub, is of particular interest. Therefore, experimental and numerical investigations of a single axial compressor stator row with varying tip gap height (tip gap height/chord length =2.0%|5.4%|6.7%) have been conducted. Comparing cases with rotating or stationary hub endwall segments upstream of the examined vanes allowed to determine the effect of the skewed and un-skewed inflow BL. The steady-state flow fields up- and downstream of the stator row were measured using five-hole pressure probes. For validation and to improve the understanding of the existing flow phenomena, 3D-Reynolds-averaged Navier–Stokes (RANS) CFD simulations using a commercial flow solver were carried out. Furthermore, analog cases with no tip gap were examined and considered in the comparisons to extend the knowledge on this BL characteristic. The results show that the BL skew has a major influence on the trajectory and size of the tip leakage vortex for the cases with tip clearance. The effect of reduction of the produced losses decreases with increasing tip gap height.

Fast direct flow simulation in porous media by coupling with pore network and Laplace models

Permeability characterises flow in porous rocks/media for upscaling, while steady-state flow fields allow analysis of reactive transport, fines migration, and tight unconventional rocks. Fast calculation of permeability and flow fields obtained from Pore Network Models (PNM) and Laplace Semi-Analytical Solvers (SAS) deviate from computationally demanding simulation of Navier Stokes Equations (NSE) due to flow and geometry simplifications. Coupling PNM/SAS with direct simulation via Lattice Boltzmann Method (LBM) provides 5--150× speed-up without accuracy loss over 100 samples from 0.7mD to 3.5D. Permeability errors in PNM/SAS show 10-20% (up to 50-70%) error. PNM shows higher variance from geometric simplifications compared to SAS which only makes flow-based assumptions. PNM/SAS errors are eliminated by coupling with LBM at a fraction of LBM-only compute cost. Steady-state conditions with PNM/SAS-LBM are reached in <2,000 timesteps, compared to LBM-only which can require >105 timesteps in tight domains such as cemented sandstone, carbonate, coal, and shale.

Periodic fluctuations of streamwise vortices in inertia-dominated intersecting flows

In the proximity of stagnation points, flow instabilities tend to arise at relatively low Reynolds numbers (Re). These instabilities often manifest as vortices that can evolve time-periodic patterns as Re is increased. These types of flows are well studied in cases for which the stagnation point is fixed on an obstacle and the resulting vortices are in the spanwise direction (e.g., the von Kármán vortex street). However, they are less understood in intersecting flows, where the stagnation point is not wall-attached and the resulting vortices are stretched by the flow in the streamwise direction. In this study, quantitative flow velocimetry measurements and three-dimensional numerical simulations are used to characterize two types of steady vortical flow fields in rectangular, intersecting microfluidic geometries with different aspect ratios, α, of the intersecting channels. We show that by changing α, it is possible to precisely tune the features of the steady-state vortical flow field, including the number of vortices, their relative rotation direction, nearby circulation areas, and even vortex core structure. The unique steady-state features determine the onset parameters, dynamics, and frequency of time-periodic fluctuations that develop at higher Re. Our results can be directly applied for enhancing the control over the vortical motion of transported fluids in inertial microfluidics and lab-on-a-chip devices. Additionally, these findings contribute to the fundamental knowledge on vortical motion with the potential to improve the control over vortex-induced vibrations on obstacles in both terrestrial and marine environments.

Large Eddy Simulation of the Transitional Flow Around the SD7003 Airfoil and Application to Blade–Vortex Interaction

The transitional flow around the SD7003 airfoil at $$\alpha = 8^\circ$$ , $${\text { Re }}= 60,000$$ and $${\text { Ma }}= 0.2$$ was investigated employing p-adaptive large eddy simulations in a Discontinuous Galerkin (DG) framework. This test case is particularly challenging since a laminar separation bubble (LSB) with transition and reattachment of the turbulent boundary layer has been observed. The results obtained with the dynamic anisotropic model have been compared with experimental measurements and other numerical results available in literature. The polynomial adaptivity technique confirmed its capability to correctly represent the flow with a great saving in the computational cost. The results are close to experimental measurements thanks to the capability of the subgrid model to capture the energy backscatter from the subgrid scales. Starting from the statistically steady state flow field obtained, the viscous, parallel, Blade-Vortex Interaction (BVI) has been studied in the same numerical framework. A modelled vortex has been superimposed to the developed flow around the SD7003 airfoil and the dynamic p-adaptivity has been successfully employed to capture its advection over time. The loads have been recorded and compared with a reference simulation without the vortex. While the drag rapidly comes back to its steady-state value, the transients for lift and moment coefficients are longer because of the effect of the vortex on the LSB.

Stabilized motion of a freely falling bristled disk

Several tiny insects have peculiar porous wings composed of many bristles and perform an interesting passive flight known as parachuting. Despite numerous studies on the freefall of objects such as disks, the aerodynamic principles of the effects of a bristled configuration on the parachuting motion under external disturbances remain unexplored. Here, we experimentally investigate freely falling bristled disks over a wide range of Reynolds numbers by changing the number of bristles and the initial orientation angle and compare their kinematics with those of a full circular disk with no bristles. Given the same diameter and moment of inertia, bristled disks with a smaller area have a steady-state flow field similar to that of a circular disk by virtue of the presence of a fully formed virtual fluid barrier at low-Reynolds numbers. However, in the initial transient phase after release, the bristled disks show different damped oscillatory motions from a circular disk. Regardless of their initial orientation angle, the lateral and angular deviations of the bristled disks are smaller than those of the circular disk, producing a more stable freefall. This trend is also observed even for higher Reynolds numbers, where the bristled wings are known to be ineffective from the perspective of aerodynamic performance. By considering the vorticity fields around the disk, we suggest two vortex-related mechanisms that account for the stable falling of the bristled disk, namely, the formation of more symmetric vortex structures and the location of vortex cores closer to the disk center.

Numerical Simulation of Instabilities in the Boundary-Layer Transition Experiment Flowfield

The development of disturbances in the boundary-layer transition (BoLT) flight experiment flowfield is investigated using a recently developed “quiet direct numerical simulation (DNS)” approach. By using a combination of low-dissipation numerics and a novel shock capturing method, numerical noise is significantly reduced, enabling the simulation and analysis of early stages of the transition process that are governed by the linear growth of small-amplitude disturbances. The freestream conditions of the present simulations correspond to experiments conducted in the Purdue Boeing/U.S. Air Force Office of Scientific Research Mach 6 quiet tunnel under quiet flow at a unit Reynolds number of . First, the steady-state flowfield is computed and then compared to infrared images, demonstrating excellent agreement with experimentally measured steady streamwise wall heat flux streaks. Next, an unsteady numerical simulation is performed with continuous stochastic forcing to excite boundary-layer instabilities. Two-dimensional time-series snapshots of the disturbance flowfield are saved at several streamwise locations. Sparsity-promoting dynamic mode decomposition (SPDMD) is used to extract dominant modes from the snapshot sequences. The frequencies of dominant modes are compared to power spectral densities obtained from wall pressure fluctuations measured in the experiments. Based on numerical and experimental data, three distinct instabilities in the BoLT flowfield are identified. The quiet DNS approach used in conjunction with controlled disturbances to excite instabilities, as well as SPDMD to analyze them, represents a new high-fidelity method of investigating stability and transition in complex three-dimensional flowfields.

Study on Aerodynamic Noise Numerical Simulation and Characteristics of Safety Valve Based on Dipole and Quadrupole

Aiming at the problem that it is difficult to accurately predict the aerodynamic noise in the safety valve exhaust process, a new numerical simulation method that comprehensively considers the dipole sources and the quadrupole sources is proposed. The RNG k–e model is used to simulate the steady-state flow fields, LES numerical method is used to simulate the transient flow, and then the unsteady disturbances are used as source terms in the generalized FW–H solver incorporating the dipole and quadrupole terms to solve for the acoustic field. This simulation method is used to calculate the exhaust noise of the safety valve under six different operating conditions, the sound source characteristics of the exhaust noise of the safety valve are analyzed, and the safety valve exhaust test of different working conditions was carried out. The results show that the relative errors of total sound pressure level between simulation and test does not exceed 5% under different exhaust pressures and different opening heights of the safety valve flap. By comparing the total sound pressure level logarithmically superimposed with the total sound pressure level of the dipole and the quadrupole, the sound source characteristics of the aerodynamic noise of the safety valve are mainly dominated by the sound source of the quadrupole. As the opening height of the safety valve flap and exhaust pressure increase, the total sound pressure level of the safety valve exhaust noise increases, while the relative errors between the simulation results and test data decrease. The proposed simulation method can be accurately applied to the prediction of the safety valve exhaust noise, and the prediction accuracy of this simulation method also increases when the opening height of the safety valve flap and exhaust pressure increase.

Abstract 4263: Characterization of patient-specific drug delivery for breast cancer using image-guided computational fluid dynamics

Abstract Introduction: A tumor's blood supply and interstitial flow play an essential role in tumor growth, invasion, and treatment response. We have developed a methodology that employs quantitative MRI data to constrain a patient-specific, computational fluid dynamics (CFD) model of blood flow and interstitial transport within breast tumors. The dynamics of solute transport are characterized based on steady state flow fields, so that delivery of oxygen, nutrients, or therapies through the circulation can be estimated. It is a fundamentally new way to characterize breast tumor hemodynamics using MRI. Method: Eleven malignant and five benign lesions from 12 patients were included in this study. Vessel segmentation and tracking were performed to reconstruct the whole breast vasculature and to identify vessels feeding or draining tumors. Ultrafast dynamic contrast-enhanced MRI and diffusion-weighted imaging data were analyzed to estimate the bolus arrival time, Ktrans (volume transfer coefficient), and ADC (apparent diffusion coefficient); these data were used to spatially assign flow direction, local vascular permeability, and tissue density, respectively. The model of steady state flow was described by three components: 1) blood flow following Poiseuille's law, 2) interstitial flow following Darcy's law, and 3) flux transmitted across the vascular walls following Starling's law. The behavior of drug delivery was described by an advection-diffusion equation in the interstitial tissue, with the profile of the vascular bolus as a source term. The whole system was solved with a 1D-3D coupled implementation. At the end of analysis, the tracer's propagation through the tissue-of-interest was visualized and hemodynamic characteristics are derived to compare the malignant and benign lesions. Result: Visualization of the time-resolved distribution and propagation of solute demonstrated the intratumoral heterogeneity of accessibility to drugs. Furthermore, we are currently calculating the spatially-resolved accumulation, wash-in rate, and infiltration duration of different drugs for each lesion, so that a quantitative comparison can be performed between malignant and benign lesions. Conclusion: We have developed a computational model, informed by patient-specific MRI data, to simulate the blood supply, interstitial fluid environment, and intratumorally heterogeneous access to therapies for breast tumors. It represents the first methodology of integrating CFD with patient specific MRI data for quantifying the spatiotemporally resolved drug propagation as well as the entire pressure and flow fields within the breast. NCI U01CA142565, U01CA CA174706, and R01 CA218700. CPRIT RR160005. Citation Format: Chengyue Wu, David A. Hormuth, Federico Pineda, Gregory S. Karczmar, Robert D. Moser, Thomas E. Yankeelov. Characterization of patient-specific drug delivery for breast cancer using image-guided computational fluid dynamics [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4263.

Numerical Study of Shock Train in the Isolator of Scramjet Engine

The isolator of scramjet engine has to separate the combustor from the inlet so that the scramjet can keep working stably. The steady-state flow field structure, the shock train shape and the starting position of the symmetrical model of isolator under different backpressure ratio are obtained by numerical simulation of commercial software fluent. Using the user-defined function to simulate the pressure fluctuation caused by the irregular heat release in the combustion chamber, the motion of the shock train in the isolation section is obtained. It is found that the start position of the shock train is larger than that of the steady state simulation, which provides a reference for the design of the combustion chamber.

Modelling the Dynamics of Granular Particle Interactions in a Vortex Reactor using a Coupled DPM-KTGF Model

In this work, a shear-driven two-phase particulate flow of monodispersed and polydispersed granular materials has been studied experimentally and numerically as a function of solids concentration and restitution coefficients for different operating speeds N (70 -130 rpm) in a lab-scale rotor-stator agglomeration reactor. A coupled computational fluid-particle dynamics (CFPD) model was developed consisting of a steady-state flow field of the continuous phase coupled to a transient particle tracking of the discrete phase. This was achieved via a one-way coupling between the continuous and the discrete phase by including the effect of drag, lift, pressure gradient, virtual mass forces, as well as granular collisional forces in describing the particle-particle, particle-wall and the fluid-particle interactions. The spatiotemporal evolution of the flow pattern, discrete phase properties, and influence of the operating conditions on the granular properties were characterized. The validation of the numerical model developed in this study was carried out based on the theoretical analysis of the rotor-stator flow and the PIV flow measurements. The results showed that the particle sizes were uniformly distributed within the reactor after steady-state conditions, while a small region of high particle concentration was observed near the rotor due to low vorticity and turbulent intensity around the region. In terms of the operating conditions, the restitution coefficients and the operating speeds do not have a significant influence on the granular properties apart from the small region around the shaft where there is a correlation between these parameters. The particle sizes, however, show a positive correlation with the granular properties. Also, a wider particle size distribution was observed axially towards the stator, which might be attributed to the pumping effect of the Batchelor flow in this direction. It was also concluded that the discrete phase velocity does not seem to vary significantly with the restitution coefficients. Furthermore, the vertical velocity and vorticity profiles give a reasonably good agreement between the CFPD model predictions and PIV measurements. The minor observed deviations were mainly due to some of the experimental limitations rather than the robustness of the CFPD model or the numerical code.

Effects of upscaling temporal resolution of groundwater flow and transport boundary conditions on the performance of nitrate-transport models at the regional management scale

Managed aquifer recharge and changes in crop type or nutrient management on agricultural lands are promising approaches to address groundwater quality degradation by nitrate. Tools to assess nonpoint-source contaminant transport are needed to better understand the interaction between agricultural management practices and long-term nitrate dynamics in groundwater basins. This study investigates the impact of time-resolution upscaling of groundwater flow stresses (i.e., recharge, pumping, and evapotranspiration rates) on the long-term prediction of nitrate transport at the regional scale. A three-dimensional, monthly transient flow and nitrate-transport model using MODFLOW and MT3D is applied as the reference simulation. The reference model results are compared to temporally upscaled models with (1) upscaled annual-averaged flow and transport stresses and (2) steady-state flow stresses, across different management scenarios. Models with annual-averaged flow and nitrate-loading stresses were found to be the best alternative to the reference model. However, employing a steady-state flow field to parameterize transient transport models, using a time series of spatially variable annual total contaminant loading, provides a useful alternative to predict the trend and variability of nitrate-concentration breakthrough curves at wells across the regional scale and to differentiate the effects of various agricultural management scenarios, if the history of the source contaminant mass is known. The difference between concentrations resulting from steady-state-flow versus transient-flow models is less than 2 mgN/L for nearly 75% of shallow groundwater cells in the model. However, the steady-state-flow-model-based transport simulation does not capture short-term oscillations of nitrate concentrations in pumping wells at the local scale.

Effect of wavy fin usage on thermal performance of heat exchanger used in combi boilers

In this study, performance of a heat exchanger used in combi boilers was investigated numerically for different fin geometries. Analyses were performed at the boiler operation conditions. A commercial CFD software package, FLUENT, was used for numerical simulations. The 3-D steady-state turbulent flow field analysis was carried out and k-? model was preferred as the turbulence model. In the analysis, it was assumed that the heat transfer phenomenon occurred both by conduction and convection. Flat fin geometry was taken as a reference for the investigation. Variation of the heat transfer and pressure drop values for the wavy fin were compared with the reference geometry. The wave angle and wave radius were taken as the parameters for the wavy fins. For different fin geometries: the outlet temperaTure of the combustion gases, the heat transfer to the water, and the pressure drop were calculated and the results were presented. Compared with flat fin, average decrease for the outlet temperature of hot gases was obtained as 4 K and average increase for the heat transfer to the water was calculated as 0.68 W. On the other hand, the average pressure drop in the heat exchanger with wavy fins was about 70% higher than the flat fin.

Simplified numerical simulation model for hydroxyl ammonium nitrate-based monopropellant rocket engines

A simplified model is proposed to simulate the working process of hydroxyl ammonium nitrate-based monopropellant rocket engines. The porous medium model and volume-of-fluid model are used to solve for the internal flow field of a monopropellant engine containing a catalyst bed to emphasize the establishment of a propellant decomposition model. The decomposition process is assumed to be separable into mass transfer and quick energy release processes. The mass transfer process is described by a two-stage decomposition model that combines catalytic and thermal decompositions according to temperature. This paper explains how to implement the two-stage decomposition model by using a titration experiment and thermal decomposition data. A detailed example is provided involving the calculation of the steady-state flow field of a 150-N monopropellant rocket engine in FLUENT. The results obtained using only the catalytic decomposition model and the two-stage decomposition model were compared with those of hot-fire tests, and show that the two-stage decomposition model is accurate. The combustion chamber pressure obtained from two- and three-dimensional simulations for the flow field of the engine agreed with the results of hot-fire tests. The calculated external wall temperature of the lower catalyst bed was slightly higher than the measured temperature, whereas the external wall temperature of the upper catalyst bed was close to the measured values.

An analytical pattern-based method for estimation of a near-surface tornadic wind field

Existing methods of in-situ measurement struggle to capture near-surface wind speeds during a tornado. The demand for accurate near-surface wind fields for the seemingly imminent tornado based design requires new methods of near-surface wind speed estimation, some of which use damage survey data. Information on tree-fall patterns included in damage survey data can and have been used as an indicator of the wind field. Thus, this paper develops an improved analytical method based on tree-fall patterns to estimate the near-surface wind field. This improved analytical model generates a translational steady-state tornado flow field under a superposition of a translational field and a rotational field. The rotational field can be generated by tornado vortex models, then the best-fit parameters for the selected vortex model to create a near-surface translational steady-state tornadic field. This wind field can be estimated on the basis of tornado-induced tree-fall patterns obtained by aerial photos. In this paper, an application is developed with the tree-fall survey data of the 2011 Joplin, MO tornado and used the Rankine vortex model.

Upscaling of Regional Scale Transport Under Transient Conditions: Evaluation of the Multirate Mass Transfer Model

AbstractRegional scale transport models are needed to support the long‐term evaluation of groundwater quality and to develop management strategies aiming to prevent serious groundwater degradation. The purpose of this study is to evaluate the capacity of a previously developed upscaling approach to adequately describe the main solute transport processes, including the capture of late‐time tails under changing boundary conditions. Potential factors that impact the performance of upscaling methods, including temporal variations in mass transfer rates and mass distributions, were investigated. Advective‐dispersive contaminant transport in a 3‐D heterogeneous domain was simulated and used as a reference solution. The equivalent transport under homogeneous flow conditions was then evaluated by applying the multirate mass transfer (MRMT) model. The random walk particle tracking method was used to solve the solute transport for heterogeneous and homogeneous MRMT scenarios under steady state and transient conditions. The results indicate that the MRMT model can capture the tails satisfactorily for plumes transported with ambient steady state flow fields at all studied scales using the same parameters. However, when the boundary conditions change in either local, plume, or regional scale, the mass transfer model calibrated for transport under steady state conditions cannot accurately reproduce the tailings observed for the heterogeneous scenario. The deteriorating impacts of transient boundary conditions on the upscaled model are more significant for regions where the flow fields are dramatically affected, which highlights the poor applicability of the MRMT approach for complex field settings. This finding also has implications for the suitability of other potential upscaling approaches.

Influence of geometric configuration on aerodynamics of streamlined bridge deck by unsteady RANS

Long-span bridge decks are often shaped as streamlined to improve the aerodynamic performance of the deck. There are a number of important shaping parameters for a streamlined bridge deck. Their effects on aerodynamics should be well understood for shaping the bridge deck efficiently and for facilitating the bridge deck design procedure. This study examined the effect of various shaping parameters such as the bottom plate slope, width ratio and side ratio on aerodynamic responses of single box streamlined bridge decks by employing unsteady RANS simulation. Steady state responses and flow field were analyzed in detail for wide range of bottom plate slopes, width and side ratios. Then for a particular deck shape Reynolds number effect was investigated by varying its value from 1.65x104 to 25x104. The aerodynamic response showed very high sensitivity to the considered shaping parameters and exhibited high aerodynamic performance for a particular combination of shaping parameters.

Characterizing transport and deposition of particulate pollutants in a two-zone chamber using a Markov chain model combined with computational fluid dynamics

• Markov chain model combined with CFD for multi-zone space proposed. • Exposure levels and deposition rates of particulate pollutants analyzed. • Proposed model may be of practical use for obtaining real-time predictions. Understanding the distribution and spread of indoor airborne contaminants between rooms in a multi-zone space is crucial for protecting human health and indoor environmental control. Predicting the transmission of suddenly released particulate pollutants from one room to another in a rapid and precise manner is important for reducing or even eliminating the risk of cross contamination between occupants. In this study, we developed a modified Markov chain model that considers the effect of gravity to predict the dispersion and deposition of aerosol particles in a two-zone chamber. To perform particle phase simulations, the proposed model couples the data obtained from a steady-state flow field using the computational fluid dynamics (CFD) software Fluent with some codes that we developed in the MATLAB environment. Two examples based on previously reported experimental data were used to validate the proposed model. The results indicate that the proposed model is suitable for modeling the dynamic processes where airborne particles are released from constant and pulsed contaminant sources in multi-zone spaces with reasonable accuracy and computational efficiency. After analyzing particle exposure in the two-zone chamber, we found that the accumulated exposure level in the zone with the constant contaminant source always had a higher rate of increase than the other zones. However, the accumulated exposure level for the pulsed (instantaneous) source was inversely proportional to the air exchange rate for all zones. Compared with traditional CFD models and multi-zone models, our proposed model can balance the accuracy and efficiency when predicting the spread of particulate contaminants in multi-zone spaces by choosing appropriate grid resolution (s).

Analyzing Influence of Ignition Gas Flow Pipe of Igniter on Working Process

Based on gas dynamics and computational fluid dynamics, the numerical simulation of the steady-state flow field of igniter working in the two conditions was conducted with FLUENT. The numerical simulation results were validated by experiments. Influences of ignition gas flow pipe on the igniter's working performance were analyzed on the basis of test validation. The analysis results show that the combustion chamber pressure has atmospheric pressure and that the igniter works with ignition gas flow pipe. The velocity of throat is lower than the speed of sound and the sonic position moves to the position of ignition gas flow pipe; the velocity, pressure and temperature of throat increase; but the flux, pressure and temperature of outlet decrease. Under the different conditions of combustion chamber pressure, the outlet velocity, pressure, temperature and flux have a stable section; but the flux decreases.

Predicting thermophoresis induced particle deposition by using a modified Markov chain model

Thermophoresis is considered as one of the major causes leading to deposition of suspended submicron aerosols with the presence of temperature gradient. Prompt obtaining of information about particle deposition and spatial distribution is crucial to environment control. This study proposed a modified Markov chain model to include the effect of thermophoresis. A steady-state flow field and a constant temperature field are firstly established by using Computational Fluid Dynamics (CFD) tools. Then the data of flow and temperature fields are exported out as data files, which will be used by the proposed model to realize the particle phase simulation. A horizontal steady-state laminar duct flow case is used to validate the model. Results show that the proposed model is able to efficiently predict thermophoresis induced particle deposition and dispersion with reasonable accuracy. Detailed information also indicate that the particle deposition efficiency is dependent on both temperature gradients and particle diameters. However, the beginning of the particle escape (if any) is irrelevant to those two parameters. The highest deposition efficiency on the deposition surface is found to gradually increase over time and the location of highest deposition efficiency (peak) moves along with the main flow. The average speed of the moving peak is inversely proportional to temperature gradient, but the ultimate deposition efficiency is still proportional to temperature gradient. The proposed model is deemed a practical method in predicting aerosol particle deposition/transport as well as contaminant control in non-isothermal environment.

Influence of Separation Interference Method on Aerodynamic Responses of a Pentagonal Shaped Bridge Deck

Long-span bridges often exhibit vibration under wind action. Various aerodynamic countermeasures have been developed over the years to enhance the aeroelastic responses of the long-span bridge deck and Separation Interference Method (SIM) is one of these. Engineers should have sound knowledge about the flow mechanism of the aerodynamic countermeasures of the bridge deck for further improvement of the aerodynamic responses and better design of the bridge deck. In the present study, a numerical investigation was carried out to disclose the flow mechanism of SIM on a pentagonal bridge deck. Simulation was conducted by using unsteady RANS for a pentagonal bridge deck with and without SIM techniques and their aerodynamic responses were compared. In the first part performance of unsteady RANS was evaluated to predict the dynamic responses for a pentagonal bridge deck. Then, the steady state responses and flow fields were explored for a bridge deck with and without SIM. Later, the dynamic responses such as flutter derivatives and unsteady pressure characteristics were evaluated and compared. It was found that SIM can improve the aerodynamic responses of the bridge deck. The addition of the curb affected the flow field around the bridge deck and the important flow features noticeably. The leading-edge top and bottom surface separations and the trailing-edge bottom surface separation are the most significant flow features to control both the steady state and dynamics responses of the bridge deck.