Elevated Turbulence Research Articles

Large-scale dust explosions in vessel-pipe systems

This study investigates dust explosions in vessel-pipe systems to develop a better understanding of dust flame propagation between interconnected vessels and implications for the proper application of explosion isolation systems. Cornstarch dust explosions were conducted in a large-scale setup consisting of a vented 8-m3 vessel and an attached pipe with a diameter of 0.4 m and a length of 9.8 m. The ignition location and effective dust reactivity were varied between experiments. The experimental results are compared against previous experiments with initially quiescent propane-air mixtures, demonstrating a significantly higher reactivity of the dust explosions due to elevated initial turbulence, leading to higher peak pressures and faster flame propagation. In addition, a physics-based model developed previously to predict gas explosion dynamics in vessel-pipe systems was extended for dust combustion. The model successfully predicts the pressure transients and flame progress recorded in the experiments and captures the effects of ignition location and effective dust reactivity.

Large Eddy Simulation of Transitional Separated Flow Over a Low Reynolds Number Cambered Airfoil

Abstract The accurate simulation of the aerodynamic behavior of low Reynolds number (Re) cambered airfoils requires the ability to capture the transitional separated boundary layer (BL) that occurs naturally on the surface of the airfoil. In this study, simulations are performed using a modern cambered airfoil designed for use in low Re applications, which are an advancement from previous studies using flat plate geometries or symmetric NACA airfoils. The cambered SD 7037 airfoil is simulated using wall-resolved large eddy simulation (LES) at a modest Re of 4.1×104 and at 1 deg, 5 deg, and 7 deg angles of attack (AOAs), with results validated against experimental data. Simulated predictions of pressure and skin friction coefficients clearly capture the correct location of the laminar separated bubble (LSB) which forms during the natural BL transition process. Sensitivity to elevated inflow turbulence is found to cause early BL reattachment at higher AOAs without impacting the location of BL separation. An integral BL analysis verifies the accuracy of the simulated velocity profiles against experimental values. The scale of horseshoe structures visualized in the transitional BL is larger in comparison to airfoil chord length than what is seen in previous simulations at Re of the order of 105, which highlights the importance of investigating cambered airfoils at a modest Re.

Surface layer response to heterogeneous tree canopy distributions: roughness regime regulates secondary flow polarity

Large-eddy simulation was used to model turbulent atmospheric surface layer (ASL) flow over canopies composed of streamwise-aligned rows of synthetic trees of height, $h$ , and systematically arranged to quantify the response to variable streamwise spacing, $\delta _1$ , and spanwise spacing, $\delta _2$ , between adjacent trees. The response to spanwise and streamwise heterogeneity has, indeed, been the topic of a sustained research effort: the former resulting in formation of Reynolds-averaged counter-rotating secondary cells, the latter associated with the $k$ - and $d$ -type response. No study has addressed the confluence of both, and results herein show secondary flow polarity reversal across ‘critical’ values of $\delta _1$ and $\delta _2$ . For $\delta _2/\delta \lesssim 1$ and $\gtrsim 2$ , where $\delta$ is the flow depth, the counter-rotating secondary cells are aligned such that upwelling and downwelling, respectively, occurs above the elements. The streamwise spacing $\delta _1$ regulates this transition, with secondary cell reversal occurring first for the largest $k$ -type cases, as elevated turbulence production within the canopy necessitates entrainment of fluid from aloft. The results are interpreted through the lens of a benchmark prognostic closure for effective aerodynamic roughness, $z_{0,{Eff.}} = \alpha \sigma _h$ , where $\alpha$ is a proportionality constant and $\sigma _h$ is height root mean square. We report $\alpha \approx 10^{-1}$ , the value reported over many decades for a broad range of rough surfaces, for $k$ -type cases at small $\delta _2$ , whereas the transition to $d$ -type arrangements necessitates larger $\delta _2$ . Though preliminary, results highlight the non-trivial response to variation of streamwise and spanwise spacing.

Diurnal impact of atmospheric stability on inter-farm wake and power generation efficiency at neighboring onshore wind farms in complex terrain

Enhancing the power production efficiency of large-scale wind farms is challenging for onshore wind power due to the variability of atmospheric conditions. This work aims to study the impact of atmospheric stability on the inter-farm wake pattern, topographic effect, and power production changes at two neighboring wind farms in Hami City, Xinjiang of China over complex terrain. The results show a discernible diurnal cycle property. At night in a stable layer with hindered mixing, the inter-farm wake persists around 20 km downstream, and the greatest relative wind deficit increases by 8%. However, during the daytime unstable layer with elevated turbulence, shows a limited deficit and recovers about 6 km downstream. Accordingly, a mean relative power production reduction of 17% is subjected to the downwind farm at night, about a factor of 3 greater than that at daytime, when the mean value is only 6%. Interestingly, the largest power production losses are experienced with a larger range between maximum and minimum before dawn and after dusk due to the notable inter-farm wake with a streaky structure related to the large coherent buoyant caused by the tendency of heat flux over the complex terrain. Moreover, the topographic speed-up in the stable layer outperforms that in unstable conditions.

Experimental Investigation of Air Bubble Curtain Effects on Water Wave Field

This paper studies the effects of an air bubble curtain on surface water waves. Water particle velocities and free surface elevations were measured simultaneously at two cross-shore locations downstream of the air bubble curtain. Measurements were carried out for regular waves using different air bubble curtain configurations. Free surface elevations were measured using resistive gauges and the instantaneous velocities were acquired using an Acoustic Doppler Velocimeter (ADV). The characteristics of the free surface elevation time series, velocity field and turbulence are analyzed and discussed. The free surface elevation was found to be attenuated by the air bubble curtains. The phase averaged velocity profiles also depict the effect of the air bubbles in the flow field by generating milder longitudinal velocities (u) and by increasing the transverse component of the velocity (w). The increase in the turbulence intensity and the different energy spectrum produced by the air bubble curtain is also observed. The experimental results indicate that the thickness of the air bubble curtain and the total air flow rate affects the wave field.

Effect of the Axial Casing Groove Geometry on the Production and Distribution of Reynolds Stresses in the Tip Region of an Axial Compressor Rotor

AbstractStereo-PIV data are used for investigating the effect of axial casing groove (ACG) geometry on the distribution, evolution, and production rates of turbulent kinetic energy (TKE) and Reynolds stresses near a rotor tip. The ACGs delay the onset of stall by entraining the tip leakage vortex (TLV) and cause periodic changes to incidence angle. These effects are decoupled using semicircular, U-shaped, and S-shaped grooves that have similar inlets, but different outflow directions. Most TKE distribution trends can be explained by the local turbulence production rates, elucidating the different mechanisms involved and providing a unique database for turbulence modeling. Interaction of the tip flow with the ACGs modifies the highly anisotropic and inhomogeneous passage turbulence. In all cases, the TKE is high in the TLV center and shear layer connecting the TLV to the rotor tip. At prestall flowrate, TLV entrainment reduces the passage turbulence level, but introduces elevated turbulence in the corner vortex formed at the downstream corner of grooves, and in shear layers developing at the exit from grooves. The location of peaks and the dominant components vary among grooves. Near the best efficiency point, interactions of the TLV with the circumferentially negative outflow from the U and semicircular ACGs generate high turbulence levels, which extend deep into the passage. In contrast, interactions with S grooves are limited, resulting in a substantially lower turbulence level. Accordingly, the S groove maintains the untreated endwall efficiency, while the U and semicircular grooves reduce the peak efficiency.

Characterizing the Seasonal Variability of Hypolimnetic Mixing in a Large, Deep Lake

AbstractIn this study, we report on turbulent mixing observed during the annual stratification cycle in the hypolimnetic waters of Lake Michigan (USA), highlighting stratified, convective, and transitional mixing periods. Measurements were collected using a combination of moored instruments and microstructure profiles. Observations during the stratified summer showed a shallow, wind‐driven surface mixed layer (SML) with locally elevated dissipation rates in the thermocline () potentially associated with internal wave shear. Below the thermocline, turbulence was weak () and buoyancy‐suppressed ( < 8.5), with low hypolimnetic mixing rates () limiting benthic particle delivery. During the convective winter period, a diurnal cycle of radiative convection was observed over each day of measurement, where temperature overturns were directly correlated with elevated turbulence levels throughout the water column (; ). A transitional mixing period was observed for spring conditions when surface temperatures were near the temperature of maximum density (TMD3.98) and the water column began to stably stratify. While small temperature gradients allowed strong mixing over the transitional period (), hypolimnetic velocity shear was overwhelmed by weakly stable stratification (; ), limiting the development of the SML. These results highlight the importance of radiative convection for breaking down weak hypolimnetic stratification and driving energetic, full water column mixing during a substantial portion of the year (>100 days at our sample site). Ongoing surface water warming in the Laurentian Great Lakes is significantly reducing the annual impact of convective mixing, with important consequences for nutrient cycling, primary production, and benthic‐pelagic coupling.

Heat transfer characteristic of a fully cooled turbine vane

To evaluate the heat transfer performance of a fully cooled turbine vane, an experiment was conducted in the low-speed wind tunnel using transient liquid crystal technology. The test vane was fabricated with 18 rows of cylindrical holes, which were supplied by two plenums. In these experiments, three mass flow ratios of 5.5%, 8.4%, and 12.5%, three turbulence intensities of 2%, 9%, and 15%, three Reynolds numbers of 300000, 400000, and 500000, two density ratios of 1.0 and 1.5 were tested. The results show that the heat transfer coefficient in the leading edge is much higher than the pressure and suction side due to the direct impact of the mainstream and the severe mainstream and injection mixing. The increased mass flow ratio significantly increases the heat transfer coefficient over the entire vane surface by 3.6%–71.3%, and the elevated turbulence intensity enhances the heat transfer coefficient by 5%–45% on the suction side and the rear half of the pressure side. The higher Reynolds number causes the thinner boundary layer and the higher velocity near the wall, which results in the Nusselt number increases by 52% in the case of increasing the Reynolds number from 300000 to 500000. Additionally, the heavier coolant leads to a slightly reduced heat transfer coefficient because of the lower injection penetration.

Mechanisms of Lateral Spreading in a Near-Field Buoyant River Plume Entering a Fjord

Observations collected from a fast-flowing buoyant river plume entering the head of Doubtful Sound, New Zealand, were analysed to examine the drivers of plume lateral spreading. The near-field plume is characterised by flow speeds of over 2 ms−1, and strong stratification (N2 > 0.1 s−2), resulting in enhanced shear which supports the elevated turbulence dissipation rates (ϵ > 10−3 W kg−1). Estimates of plume lateral spreading rates were derived from the trajectories of Lagrangian GPS surface drifters and from cross-plume hydrographic transects. Lateral spreading rates derived from the latter compared favourably with estimates derived from a control volume technique in a previous study. The lateral spreading of the plume was driven by a baroclinic pressure gradient toward the base of the plume. However, spreading rates were underestimated by the surface drifters. A convergence of near-surface flow from the barotropic pressure gradient concentrated the drifters within the plume core. The combination of enhanced internal turbulence stress and mixing at the base of the surface layer, and the presence of steep fjord sidewalls likely reduced the rate of lateral spreading relative to the theoretical spreading rate. The estimates of plume width from the observations provided evidence of scale-dependent dispersion which followed a 4/3 power law. Two theoretical models of dispersion, turbulence and shear flow dispersion, were examined to assess which was capable of representing the observed spreading. An analytical horizontal shear-flow dispersion model generated estimates of lateral dispersion that were consistent with the observed 4/3 law of dispersion. Therefore, horizontal shear dispersion appeared to be the dominant mechanism of dispersion, thus spreading, in the surface plume layer.

Numerical Investigation of Turbulent Junction Flows

Turbulent junction flows are known to exhibit a bimodal behavior of the horseshoe vortex that can be described by a random switching between a zero-flow and a backflow mode. The physical mechanism that causes the bimodal behavior is not well understood. Large-eddy simulations of a canonical junction flow geometry, the Rood wing, were carried out for a Reynolds number based on approach flow velocity and maximum thickness of 7000, and the junction flow physics were analyzed. The approach boundary-layer profile, mean flow data, and turbulent statistics obtained from the simulation are in good agreement with measurements at Penn State University. The present results for clearly exhibit a bimodal behavior that is characterized by a forward and backward motion and intermittent loss of coherence of the horseshoe vortex. Instantaneous flow visualizations reveal that the interaction of pockets of elevated upstream boundary-layer turbulence with the horseshoe vortex can both strengthen and weaken the horseshoe vortex. This suggests that the bimodal behavior may be triggered by the turbulent boundary layer. In addition, simulations with two different circular endwall fillets were carried out. In accordance with the literature, the fillets were found to suppress the bimodal behavior.

Tidal turbine performance and near-wake characteristics in a sheared turbulent inflow

Turbulent non-homogenous flow environments at high-energy tidal sites lead to variation in power performance of tidal stream turbines. In addition, non-uniform loading due to combined effects of shear and elevated inflow turbulence affects device survivability. In the current study, an active-grid turbulence generator is used to mimic sheared-turbulent inflow representative of the flood (low shear) and ebb tides (high shear). The performance and near-wake characteristics of a turbine model measured in the sheared-turbulent inflow conditions are compared to conditions where the flow velocity is uniform with low and elevated turbulence intensities (Ti). The sheared-turbulent inflows were observed to result in a 5–15% drop in maximum power coefficient when compared to the low Ti case. An increase of ∼30% in torque- and ∼50% in thrust- fluctuations were observed for sheared inflows. Unlike the near axisymmetric wake profiles observed for homogeneous cases, inflow shear was observed to incite asymmetry in the near-wake with an immediate impact in wake turbulence and a more gradual effect on the velocity deficit and integral length scales. The data sets are deemed valuable in calibrating computational models to better predict turbine response and optimize turbine efficiency and the complementing power take-off system.

Effects of Axial Casing Grooves on the Structure of Turbulence in the Tip Region of an Axial Turbomachine Rotor

Abstract Challenges in turbulence modeling in the tip region of turbomachines include anisotropy, inhomogeneity, and non-equilibrium conditions, resulting in poor correlations between Reynolds stresses and the corresponding mean strain-rate components. The geometric complexity introduced by casing grooves exacerbates this problem. Taking advantage of a large database collected in the refractive index-matched liquid facility at Johns Hopkins University (JHU), this paper examines the effect of axial casing grooves on the distributions of turbulent kinetic energy (TKE), Reynolds stresses, anisotropy tensor, and TKE production rate in the tip region of an axial turbomachine. The comparisons are performed at flowrates corresponding to prestall and best efficiency points of the untreated machine. Common features include high TKE near the tip leakage vortex center and in the shear layer connecting it to the blade suction side tip corner. The turbulence is highly anisotropic and inhomogeneous, with the anisotropy tensor shifting from one-dimensional (1D) to 2D and 3D structures over small distances. With the grooves, the flow structure, hence the distribution of Reynolds stresses, becomes more complex. Additional sites with elevated turbulence include the corner vortex that develops at the entrance to the grooves, and in the flow jetting out of the grooves into the passage. Consistent with trends of the production rates of normal Reynolds stress components, the grooves increase the axial but reduce the radial velocity fluctuations as the inflow and outflow from the groove interact with the passage flow. These findings might assist the development of Reynolds stress models suitable for tip flows.

Comparison of ocean vertical mixing schemes in the Max Planck Institute Earth System Model (MPI-ESM1.2)

Abstract. For the first time, we compare the effects of four different ocean vertical mixing schemes on the mean state of the ocean and atmosphere in the Max Planck Institute Earth System Model (MPI-ESM1.2). These four schemes are namely the default Pacanowski and Philander (1981) (PP) scheme, the K-profile parameterization (KPP) from the Community Vertical Mixing (CVMix) library, a recently implemented scheme based on turbulent kinetic energy (TKE), and a recently developed prognostic scheme for internal wave dissipation, energy, and mixing (IDEMIX) to replace the often assumed constant background diffusivity in the ocean interior. In this study, the IDEMIX scheme is combined with the TKE scheme (collectively called the TKE+IDEMIX scheme) to provide an energetically more consistent framework for mixing, as it does not rely on the unwanted effect of creating spurious energy for mixing. Energetic consistency can have implications on the climate. Therefore, we focus on the effects of TKE+IDEMIX on the climate mean state and compare them with the first three schemes that are commonly used in other models but are not energetically consistent. We find warmer sea surface temperatures (SSTs) in the North Atlantic and Nordic Seas using KPP or TKE(+IDEMIX), which is related to 10 % higher overflows that cause a stronger and deeper upper cell of the Atlantic meridional overturning circulation (AMOC) and thereby an enhanced northward heat transport and higher inflow of warm and saline water from the Indian Ocean into the South Atlantic. Saltier subpolar North Atlantic and Nordic Seas lead to increased deep convection and thus to the increased overflows. Due to the warmer SSTs, the extratropics of the Northern Hemisphere become warmer with TKE(+IDEMIX), weakening the meridional gradient and thus the jet stream. With KPP, the tropics and the Southern Hemisphere also become warmer without weakening the jet stream. Using an energetically more consistent scheme (TKE+IDEMIX) produces a more heterogeneous and realistic pattern of vertical eddy diffusivity, with lower diffusivities in deep and flat-bottom basins and elevated turbulence over rough topography. IDEMIX improves in particular the diffusivity in the Arctic Ocean and reduces the warm bias in the Atlantic Water layer. We conclude that although shortcomings due to model resolution determine the global-scale bias pattern, the choice of the vertical mixing scheme may play an important role for regional biases.

Time-resolved wake dynamics of finite wall-mounted circular cylinders submerged in a turbulent boundary layer

Abstract

Film Cooling Performance of a Fully Cooled Vane at High Subsonic Conditions

This work focuses on the experimental study of the heat transfer and film cooling characteristics of a fully cooled vane under high subsonic conditions; the transient heat transfer measurements with thermocouples were employed. The inlet Reynolds numbers of the cascade ranged from to and the exit Mach number was 0.8. Two freestream turbulence intensities (1.3% and 14.7%) and three mass flow ratios (5.5%, 8.4%, and 12.5%) were tested. The averaged film cooling effectiveness of the current vane with shaped holes was found to be increased by 15%–43% more than that of the vane only with cylindrical holes, and elevated turbulence intensity reduced the averaged film cooling effectiveness by 3%–26%. The heat transfer augmentation of the current vane was lower than that of the vane only with cylindrical holes. With the mass flow ratio increasing, the heat transfer augmentation gradually increased on the pressure side, whereas it was nearly kept invariable on the suction side. The net heat flux reduction results showed that the vane with shaped holes significantly improved the cooling performance, whereas elevated turbulence intensity significantly deteriorated the cooling performance.

Performance of Multiple Relay DF NLOS UVC System With CSI Imperfections

Ultraviolet communication (UVC) is emerging as an attractive alternative to the existing optical wireless communication (OWC) technologies. UVC experiences negligible noise on the earth's surface, and also has the ability to operate in non-line-of-sight (NLOS) mode, thereby making it a perfect choice for outdoor communication. However, due to strong interaction of ultraviolet waves with atmospheric particles, it suffers from a very high path loss and turbulence-induced fading, which limits UVC system's performance. We consider a decode-and-forward based cooperative relaying technique to improve the performance of NLOS UVC system, and to extend its communication range. We consider the practical case of imperfect channel state information at the receiver and derive outage probability of the system. We also consider impact of elevation angles, receiver field-of-view (FOV), and turbulence strength on the system performance. We compute the relative diversity order of the system and demonstrate its convergence through asymptotic analysis. Next, we obtain the novel expression of probability density function of the end-to-end instantaneous signal-to-noise-ratio. We use single subcarrier intensity modulation employing quadrature amplitude modulation (QAM) and derive the novel generalized analytical expressions for rectangular QAM, cross QAM, and futuristic hexagonal QAM schemes. We carry out a detailed performance study considering different system configurations and several interesting insights are highlighted, which reinforces UVC as a futuristic OWC technology. Correctness of the derived analytical expressions is confirmed using Monte-Carlo simulations.

The impact of upstream turbulence on a plane jet

The influence of upstream turbulence on the flow produced by a plane jet is investigated experimentally with hot-wire anemometry and smoke flow visualisation. An innovative active grid, where each wing can be independently controlled, is used to change the upstream turbulence conditions. Three cases are investigated: a canonical reference case, a case with the same integral scale as the reference case but an order of magnitude increase in turbulence intensity, and a case with both an order of magnitude increase in turbulence intensity and an order of magnitude increase in integral scale compared to the reference case. It is demonstrated that the wake width increases with turbulence intensity, but decreases with integral scale for constant turbulence intensity. In addition, the positional variability of the wake width is highest with high turbulence intensity and a short integral scale. Along the jet centreline, the potential core region is shorter with elevated upstream turbulence intensity; this is reflected in both the mean velocity and the variance. The decay of the centreline mean velocity is also retarded by incoming turbulence. In all, increased incoming turbulence results in increased jet spreading, and a shorter integral scale further increases the spreading.Graphic abstract

Non-isothermal mixing characteristics in the extreme near-field of turbulent jets in hot crossflow: Effects of jet exit turbulence and velocity profile

The non-reacting and reacting jets-in-crossflow (JICF) are important flow configurations for effective mixing and combustion in practical applications. Many studies in the literature examine the overall mixing characteristics of isothermal, unconfined, non-reacting JICF. This experimental study expands on our recently published work that examined mixing characteristics in the near-field of a non-reacting jet in a hot vitiated crossflow (1500 K) for the jet-to-crossflow density ratio between 3.2 and 7.8 issuing from a round jet with a fully developed turbulent pipe flow exit profile. In this study, effects of the changing jet exit velocity profile to top-hat as well as exit turbulence levels (28% and 40%) with parabolic profiles are examined. Temperature measurements were made using laser Rayleigh scattering. The jet trajectory, centerline concentration decay based on adiabatic mixing assumption, Favre-averaged scalar dissipation, and mixing time scales were compared with the previous study results. Center-plane mixing metrics indicated that top-hat and pipe flow jets behave similarly, with better near-field mixing at lower momentum flux ratios and higher density ratios. The elevated turbulence cases have a higher near-field mixing efficiency with rates that are nearly independent of momentum flux ratios above 9.3 at a constant density ratio. Scalar dissipation analysis showed that the elevated turbulence jets differ from the nominal turbulence top-hat and pipe exit jet cases with a lack of strong peaks and slightly higher upstream crossflow magnitudes. Reducing the density ratio resulted in a decrease in the windward and leeward dissipation region size and magnitude.

Characterization of anisotropic turbulence behavior in pulsatile blood flow

Turbulent-like hemodynamics with prominent cycle-to-cycle flow variations have received increased attention as a potential stimulus for cardiovascular diseases. These turbulent conditions are typically evaluated in a statistical sense from single scalars extracted from ensemble-averaged tensors (such as the Reynolds stress tensor), limiting the amount of information that can be used for physical interpretations and quality assessments of numerical models. In this study, barycentric anisotropy invariant mapping was used to demonstrate an efficient and comprehensive approach to characterize turbulence-related tensor fields in patient-specific cardiovascular flows, obtained from scale-resolving large eddy simulations. These techniques were also used to analyze some common modeling compromises as well as MRI turbulence measurements through an idealized constriction. The proposed method found explicit sites of elevated turbulence anisotropy, including a broad but time-varying spectrum of characteristics over the flow deceleration phase, which was different for both the steady inflow and Reynolds-averaged Navier–Stokes modeling assumptions. Qualitatively, the MRI results showed overall expected post-stenotic turbulence characteristics, however, also with apparent regions of unrealizable or conceivably physically unrealistic conditions, including the highest turbulence intensity ranges. These findings suggest that more detailed studies of MRI-measured turbulence fields are needed, which hopefully can be assisted by more comprehensive evaluation tools such as the once described herein.

Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies

ABSTRACT Advances in instrumentation have recently extended detailed measurements of gas kinematics to large samples of high-redshift galaxies. Relative to most nearby, thin disc galaxies, in which gas rotation accurately traces the gravitational potential, the interstellar medium (ISM) of $z$ ≳ 1 galaxies is typically more dynamic and exhibits elevated turbulence. If not properly modelled, these effects can strongly bias dynamical mass measurements. We use high-resolution FIRE-2 cosmological zoom-in simulations to analyse the physical effects that must be considered to correctly infer dynamical masses from gas kinematics. Our analysis covers a range of galaxy properties from low-redshift Milky-Way-mass galaxies to massive high-redshift galaxies (M⋆ > 1011 M⊙ at $z$ = 1). Selecting only snapshots where a disc is present, we calculate the rotational profile $\bar{v}_\phi (r)$ of the cool ($10^{3.5}\,\lt {\it T}\lt 10^{4.5}~\rm {K}$) gas and compare it to the circular velocity $v_{\rm c}=\sqrt{GM_{\rm enc}/r}$. In the simulated galaxies, the gas rotation traces the circular velocity at intermediate radii, but the two quantities diverge significantly in the centre and in the outer disc. Our simulations appear to over-predict observed rotational velocities in the centres of massive galaxies (likely from a lack of black hole feedback), so we focus on larger radii. Gradients in the turbulent pressure at these radii can provide additional radial support and bias dynamical mass measurements low by up to 40 per cent. In both the interior and exterior, the gas’ motion can be significantly non-circular due to e.g. bars, satellites, and inflows/outflows. We discuss the accuracy of commonly used analytic models for pressure gradients (or ‘asymmetric drift’) in the ISM of high-redshift galaxies.