Channel Roughness Research Articles

Heat Transfer Optimization Studies of Semi-Spherical Protrusions on a Concave Surface during Jet Impingement

Much of the literature available on heat transfer enhancement from rough surfaces concerns flat plates or channels. Studies on protruding concave surfaces are surprisingly rare though they have the potential to enhance heat transfer. Therefore, three-dimensional steady-state simulations and corresponding experimental validation is carried out for an air jet impinging on a concave surface projected with semi-spherical protrusions. By providing multiple protrusions, various geometrical configurations are studied by considering the dimensions, angular positions, and pitch between the protrusions. Each individual configuration has its own unique flow pattern which makes prediction of heat transfer complex. This motivates present study to consider entire geometrical parameters affecting heat transfer characteristics with the help of networking tool. Past investigations on protruded flat surfaces concerns random allocation of protrusions. Hence artificial neural network is employed in this study to easily predict the corresponding heat transfer value with set of few input data. Simulation results give detailed flow physics which helps in understanding the heat transfer behavior. It is observed that each protrusion is marked with high-pressure region around its uphill and negative pressure around the downhill. As the flow moves downstream, the protrusions obstruct the flow path and flow separates away as soon as it reaches center of the protrusion. A maximum heat transfer enhancement of 11% is obtained over a corresponding smooth surface.

A comparison of RANS models used for CFD prediction of turbulent flow and heat transfer in rough and smooth channels

CFD of convective heat transfer remains a challenge, especially in channels with irregular rough walls due to the complex fluid dynamics over and between these roughness elements. This study investigates the performance of four commonly utilised RANS CFD models, namely Spalart-Allmaras (SA), Realisable k-ε, SST k-ω, and Reynolds Stress Model (RSM) in estimating the velocity and temperature profile as well as the skin friction coefficient and Nusselt number in smooth and rough channels. The CFD results were compared with DNS and experimental data in the literature. The roughness-resolving approach was used for all models to resolve the realistic geometry of irregular roughness in channel flows. The smooth-channel flow study was conducted at Reτ = 500, 1000, 2000, and 5000 and Pr = 0.71. Over this range, compared to smooth-wall DNS data from literature, the RSM showed consistent and satisfactory performance in estimating the velocity and temperature profiles within 2.54% and 4.21%, respectively; leading to the skin friction coefficient and Nusselt number in the smooth channels being predicted very well within 1.94% and 2.03%, respectively. The rough-channel flow study was performed at Reτ = 240, 360, 540, 720, 1000 and Pr = 1, with computational cells 7.8 times that of the smooth channel to resolve the irregular roughness geometry. Over this range, the Realisable k-ε showed the best performance in estimating the roughness function within 6.85%, while the results of the other models were wider at uncertainty levels of up to 36.9%. Similarly, the Realisable k-ε demonstrated the best performance in estimating the skin friction and Nusselt number in rough channels within 2.76% and 9.50%, respectively, while the performance of the other models was to a wider latitude ranging between 15.62% to 26.34%. In the present study, the Realisable k-ε with enhanced wall treatment showed the best capabilities in capturing the mean flow characteristics of both smooth and rough channels; however, its usage should be approached with caution in flows at higher Reynolds numbers. RANS models are also discussed for forced convection heat transfer at high Reynolds numbers. The results of this study should be useful in CFD studies on the effects of roughness in complex geometries without the need for LES and DNS.

Surface roughness effect on dynamic wettability in imbibition process

Dynamic wetting on rough surface is important in imbibition processes in micro- and nano- channels. Due to high computational costs, the previous studies by direct numerical simulations mostly adopted two-dimensional (2D) simplifications of surface with roughness. The cutting-edge advances in high performance computing make it possible to conduct three-dimensional (3D) direct simulations. This work presents 3D simulations on channel flows with roughness on walls via the GPU-based multiphase lattice Boltzmann method (LBM). The effects from 3D roughness morphology are investigated. In contrast to the wettability alternation in 2D rough ones, the 3D rough hydrophilic surfaces remain hydrophilic and Wenzel state at even low capillary numbers (Ca). The apparent contact angle follows the hydrodynamic model on rough surfaces except for a more sensitivity to Ca. The results also indicate that the 2D simplifications overestimate the pressure drop for rough channels, while underestimate over 20% for smooth channels. Therefore, it is crucial to consider 3D structures of surface roughness for dynamic wetting in real channels.

Effect of wall roughness on flame acceleration and deflagration-to-detonation transition in a narrow channel

Numerical simulations are conducted to investigate the effect of wall roughness on flame acceleration (FA), deflagration-to-detonation transition (DDT), and detonation propagation in a narrow channel filled with stoichiometric hydrogen-air mixture. The wall roughness is determined by the element height h relative to the pipe diameter d and can be described using a dimensionless number Ra = 2h/d. A high-order numerical algorithm is employed to solve the Navier–Stokes equations on an adaptive mesh. The results show that the roughness enhances the effect of boundary layer and promotes FA and DDT. In channels with small roughness (Ra<0.1), detonation is not observed. Flame instabilities are caused by the interaction between the flame surfaces and reflected waves from the sidewalls, wrinkling of the flame front, leading to additional flame acceleration, and the production of intense pressure waves. In comparison, in channels with large roughness (Ra>0.1), vortices, shears, and even turbulence are produced in the cavity-like regions as leading shock passes over the elements. The mechanisms of the final detonation transition in the rough narrow channel are thought to be the formation of local hot spots arising from the multiple interactions of shocks with the roughness elements and viscous heating of unburned gas in the highly turbulent boundary layer.

Direct numerical simulation of coflowing rough and smooth turbulent channel flows

Turbulent channel flow with underlying rough and smooth surfaces present abreast is investigated using direct numerical simulations. Secondary roll cells, exhibiting a strong updraft in the smooth half of the channel, are observed. The roll cells have significantly attenuated the bulk flow and turbulence in the smooth half of the channel.

Modeling and investigation of fluid flow affecting thermal boundary conductance at the solid-fluid interface

Thermal conduction between solid and fluid is crucial in cooling technology based on micro and nanofluidics, while the impact mechanism of flow on interfacial thermal transport is yet to be studied due to the absence of simulation models. In this work, we propose a model to investigate the effect of fluid flow on the thermal boundary conductance between solid and fluid using molecular dynamics simulations. The present results indicate that the best way to eliminate viscous temperature rise is to control temperature by excluding velocity components along the flow direction rather than removing average velocity. The thermal conduction is insensitive to the fluid flow in atomic-smooth channel, but highly depends on the flow velocity in rough channel, where the thermal boundary conductance decreases by 11.7% when flow velocity reaches 18 m/s. The results are attributed to the variations of flow field, where the rough morphologies will disturb the parallel flow of fluid and restrain the thermal vibration of interfacial fluid. This work reveals the influence of fluid flow on interfacial thermal exchange, and the proposed model and results are helpful to improve the cooling systems based on microfluidics.

Extreme Flood Calibration and Simulation Using a 2D Hydrodynamic Model Under a Multipurpose Reservoir

Extreme floods have become common in Asian cities, with recent increases in urbanization and extreme rainfall driving increasingly severe and frequent events. Understanding the flood dynamic is essential for developing strategies to reduce risk and damage, thus ensuring the city’s protection. Channel roughness is a sensitive parameter in developing a hydraulic model for flood forecasting and flood inundation mapping. A High-resolution 2D HEC-RAS model was used to simulate the flood events of 1994, 1998, 2002, 2006, and 2015. The calibrated model, in terms of channel roughness, has been used to simulate the flood for the year 2006 in the river. The performance of the calibrated HEC-RAS-based model has been accessed by capturing the flood peaks of observed and simulated floods and computation of root mean squared error (RMSE) for the intermediated gauging stations on the lower Tapi River. Results revealed that there is good agreement between simulated and observed floods.

Inertia and diffusion effects on reactive transport with fluid-solid reactions in rough fracture flows

This study investigates the impacts of fluid inertia and solute diffusion on the reactive transport involving bimolecular fluid-solid reactions in rough channel flows. The critical role of flow fields on fluid-solid reactions is highlighted. Further, a parsimonious upscaled model that successfully captures the reactive transport process is developed.

A framework approach to address the trend and causes of flood stage change in a river reach downstream of a dam influenced by tributaries

The evaluation of the trend of flood stage changes in alluvial rivers downstream of dams is important for flood management. However, the flood stage associated with a given discharge generally is nonstationary in river reaches with multiple tributaries. This is not only because of the dam-induced shifting in the cross-sectional area and/or channel roughness but also because of the backwater induced by high flows from the tributaries. To determine the total trend of the flood stage and quantify the separate contributions of hydrological and geomorphic effects, the current study proposed a framework approach consisting of hydrological analysis and multiscenario numerical modeling. By this means, the trend in the flood stage could be distinguished from the stage oscillation driven by varying factors, including extreme hydrologic events. The effects of chronic changes, including channel incision and flow resistance increase, also were quantitatively separated. This framework was applied to the Chenglingji–Datong (CD) reach downstream of the Three Gorges Dam (TGD) in the Yangtze River, China. The results indicated that the effect of the roughness increase counterbalanced the effect of channel incision when the flow discharge was beyond the bankfull level. The backwater effect induced by tributary inflow was the major cause of the flood stage rise in recent years. The method presented in the current study provides a useful tool for managers and engineers to obtain better insight into the driving mechanisms of flood stage changes in river reaches that are downstream of dams. These findings indicate that the flood stage may not decline or may even occasionally increase, although the cross-sectional area was enlarged by channel incision. Special attention should be given to the flood risk situation in the study reach after the TGD began operation.

Simulation of Turbulent Flow Structure and Particle Deposition in a Three-Dimensional Heat Transfer Duct with Convex Dimples

In engineering applications, dust deposition on the heat transfer channel greatly reduces the efficiency of heat transfer. Therefore, it is very significant to study the characteristics of particle deposition for thermal energy engineering applications. In this study, the Reynolds stress model (RSM) and the discrete phrase model (DPM) were used to simulate particle deposition in a 3D convex-dimpled rough channel. A discrete random walk model (DRW) was used for the turbulent diffusion of particles, and user-defined functions were developed for collisions between particles and walls. An improved deposition model of rebound between particles was developed. The flow structure, secondary flow, temperature distribution, Q criterion, and particle deposition distribution in the convex-dimpled rough channel were analyzed after a study of the grid independence and a numerical validation. The results showed that these mechanisms affected the flow structure in the flow field. For tiny particles (dp ≤ 10 μm), the presence of convex dimples promoted their deposition. The rates of particle deposition in the presence of convex dimples were 535, 768, 269, and 2 times higher than in smooth channels (particle sizes of 1, 3, 5, and 10 μm, respectively). However, for large particles (dp &gt; 10 μm), although the presence of convex dimples had a certain effect on the location distribution of particle deposition, it had little effect on the deposition rates of large particles, which were 0.99, 0.98, 0.97 and 0.96 times those in the smooth channel, respectively.

Numerical simulation of turbulent flow and particle deposition in heat transfer channels with concave dimples

The efficiency of heat transfer will be significantly reduced if airborne particles deposit in the heat transfer channel. Better understandings on particle deposition characteristics in heat exchanger channel are crucial for the energy efficiency improvement. In this study, the particle deposition in a three-dimensional dimpled rough channel was simulated using the Reynolds stress model (RSM) and discrete particle model (DPM). For the turbulent diffusion of particles, the random walk model (DRW) was employed, and for the particle–wall contact, user-defined functions(UDF) are developed in this study to achieve motions such as bouncing and deposition of particles. Grid independence testing and numerical verification were followed by an analysis and study of the flow structures, secondary flow, temperature distribution, and particle deposition distribution in the dimpled rough channel. On the turbulent structure and particle deposition characteristics, the impacts of several significant parameters, including particle size, airflow velocity, the ratio of dimple depth to inner diameter (h/d), and the ratio of inner diameter of dimple to distance between dimples (d/s), were examined. The findings demonstrate that the primary mechanisms influencing the deposition characteristics of particles in dimpled channels are gravity deposition, thermophoresis force distribution, turbulence structure, secondary flow, and particle inertia, and the effects of these mechanisms change significantly with particle size. For small particles (dp ≤ 10 μm), the presence of dimples will encourage deposition; however, for large particles (dp > 10 μm), the presence of dimples will only have a little impact on the distribution of where the particles are deposited.

Investigating the Relationship between the Manning Coefficients (n) of a Perforated Subsurface Stormwater Drainage Pipe and the Hydraulic Parameters

Subsurface perforated pipes drain infiltrated stormwater runoff while attenuating the peak flow. The Manning roughness coefficient (n) was identified as a fundamental parameter for estimating roughness in various subsurface channels. Hence, in this work, the performance of a six-row non-staggered sand-slot perforated pipe as a sample of the subsurface drainage is investigated experimentally in a laboratory flume at Universiti Sains Malaysia (USM) aimed at determining the Manning roughness coefficients (n) of the pipe and assessing the relationship between the Manning’s n and the hydraulic parameters of the simulated runoff flow under the conditions of the tailgate channel being opened fully (GFO) and partially (GPO), as well as the pipe having longitudinal slopes of 1:750 and 1:1000. Water is pumped into the flume at a maximum discharge rate of 35 L/s, and the velocity and depth of the flow are measured at nine points along the inner parts of the pipe. Based on the calculated Reynolds numbers ranging from 38,252 to 64,801 for both GFO and GPO conditions, it is determined that most of the flow in the perforated pipe is turbulent, and the calculated flow discharges and velocities from the outlets under GFO are higher than the flow and velocity rates under GPO with similar pipe slopes of 1:750 and 1:1000. The Manning coefficients are calculated at nine points along the pipe and range from 0.004 to 0.009. Based on the ranges of the calculated Manning’s n, an inverse linear relationships between the Manning coefficients and the flow velocity under GFO and GPO conditions are observed with the R2 of 0.975 and 0.966, as well as 0.819 and 0.992 resulting from predicting the values of flow velocities with the equations v = ((0.01440 − n)/0.009175), v = ((0.01330 − n)/0.00890), v = ((0.02007 − n)/0.01814), and v = ((0.01702 − n)/0.01456) with pipe slopes of 1:750 and 1:1000, respectively. It is concluded that since the roughness coefficient (Manning’s n) of the pipe increases, it is able to reduce the flow velocity in the pipe, resulting in a lower peak of flow and the ability to control the quantity of storm water in the subsurface urban drainages.

Evaluating Apple iPhone LiDAR measurements of topography and roughness elements in coarse bedded streams

High resolution topographic data are necessary to understand benthic habitat, quantify processes at the water-sediment interface, and support computational fluid dynamics models for both surface and hyporheic hydraulics. In riverine systems, these data are typically collected using traditional surveying methods (total station, DGPS, etc.), airborne or terrestrial laser scanning, and photogrammetry. Recently, handheld surveying equipment has been rapidly acquiring popularity in part due to its processing capacity, price, size, and versatility. One such device is the iPhone LiDAR, which could have a good balance between precision and ease of use and is a potential replacement for conventional measuring tools. Here, we evaluated the accuracy of the LiDAR sensor and a Structure from Motion (SfM) method based on photos collected using the iPhone Cameras. We compared the LiDAR and SfM elevations to those from a high-precision laser scanner for an experimental rough water-worked gravel-bed channel with boulder-like structures. We observed that both the LiDAR and SfM methods captured the overall streambed morphology and detected large (Hs ≥ 15 cm) and macro (5 cm ≤ Hs < 15 cm) scales of topographic variations (Hs , roughness). The SfM technique also captured small scale (Hs <5cm) roughness whereas the LiDAR consistently simplified it with errors of ∼3.7 mm.

Flow and heat transfer of supercritical hydrocarbon fuel in additively manufactured cooling channels

As additive manufacturing (AM) technology has advanced, an increasing number of aero-engine cooling components are being fabricated by metal AM. However, the effects of the inherent rough surface morphology from using AM technology on the flow and heat transfer characteristics in the cooling channel are unclear. Therefore, this experimental investigation compared the flow behavior and thermal performance of supercritical hydrocarbon fuel between horizontal AM (Rz = 43.1 µm) and conventionally mechanically manufactured (CM) (Rz = 11.7 µm) mini-channels. The effects of system pressure (p), Reynolds number at the inlet (Rein), and heat flux rate (q) on the flow and heat transfer performance were evaluated. The findings indicate that heat transfer is significantly enhanced in the AM mini-channel compared to the CM channel. The thermal acceleration effect is inhibited in the AM channel owing to the rough topography. The non-dimensional roughness threshold of AM hydraulic rough channel is or lower than 2.2%. NuAM increased by approximately 16, but NuCM increased by 5 when the heat flow rate increased from 166 to 273 KW/m2. Furthermore,hAM increased by approximately 4 KW/(m2-k), but hCM only increased by approximately 2 KW/(m2-k) when the Rein increased from 6100 to 15,000. Moreover, both NuAMand NuCM decrease with increasing system pressure. Finally, the correlations between NuAM and NuCM for supercritical hydrocarbon fuel was proposed to support future research and design of aero-engine complex cooling structures.

CRITICAL ANALYSIS OF EXISTING METHODS FOR CALCULATING CHANNELS WITH HETEROGENEOUS ROUGHNESS

This article examines the application of their methods, critically analyzing the data obtained as a result of many years of research when calculating the roughness channels of the actual work performed. The value of the reduced roughness coefficient when the flow is moving is always higher than one of the largest values of the roughness coefficients that make up the channel. According to the cross-section of the channels, the general calculation formula should be generalized, taking into account the possibility of different roughness of the sole.

Bayesian calibration of a flood simulator using binary flood extent observations

Abstract. Computational simulators of complex physical processes, such as inundations, require a robust characterization of the uncertainties involved to be useful for flood hazard and risk analysis. While flood extent data, as obtained from synthetic aperture radar (SAR) imagery, have become widely available, no methodologies have been implemented that can consistently assimilate this information source into fully probabilistic estimations of the model parameters, model structural deficiencies, and model predictions. This paper proposes a fully Bayesian framework to calibrate a 2D physics-based inundation model using a single observation of flood extent, explicitly including uncertainty in the floodplain and channel roughness parameters, simulator structural deficiencies, and observation errors. The proposed approach is compared to the current state-of-practice generalized likelihood uncertainty estimation (GLUE) framework for calibration and with a simpler Bayesian model. We found that discrepancies between the computational simulator output and the flood extent observation are spatially correlated, and calibration models that do not account for this, such as GLUE, may consistently mispredict flooding over large regions. The added structural deficiency term succeeds in capturing and correcting for this spatial behavior, improving the rate of correctly predicted pixels. We also found that binary data do not have information on the magnitude of the observed process (e.g., flood depths), raising issues in the identifiability of the roughness parameters, and the additive terms of structural deficiency and observation errors. The proposed methodology, while computationally challenging, is proven to perform better than existing techniques. It also has the potential to consistently combine observed flood extent data with other data such as sensor information and crowdsourced data, something which is not currently possible using GLUE calibration framework.

Denoising Generalization Performance of Channel Estimation in Multipath Time-Varying OFDM Systems

Although Orthogonal Frequency Division Multiplexing (OFDM) technology is still the key transmission waveform technology in 5G, traditional channel estimation algorithms are no longer sufficient for the high-speed multipath time-varying channels faced by both existing 5G and future 6G. In addition, the existing Deep Learning (DL) based OFDM channel estimators are only applicable to Signal-to-Noise Ratios (SNRs) in a small range, and the estimation performance of the existing algorithms is greatly limited when the channel model or the mobile speed at the receiver does not match. To solve this problem, this paper proposes a novel network model NDR-Net that can be used for channel estimation under unknown noise levels. NDR-Net consists of a Noise Level Estimate subnet (NLE), a Denoising Convolutional Neural Network subnet (DnCNN), and a Residual Learning cascade. Firstly, a rough channel estimation matrix value is obtained using the conventional channel estimation algorithm. Then it is modeled as an image and input to the NLE subnet for noise level estimation to obtain the noise interval. Then it is input to the DnCNN subnet together with the initial noisy channel image for noise reduction to obtain the pure noisy image. Finally, the residual learning is added to obtain the noiseless channel image. The simulation results show that NDR-Net can obtain better estimation results than traditional channel estimation, and it can be well adapted when the SNR, channel model, and movement speed do not match, which indicates its superior engineering practicability.

Вплив конструктивних параметрів термоплати на гістерезис за тепловим навантаженням

The contact heat exchangers designed to remove heat from the cooled devices are used in mechanically pumped two-phase loops of thermal management systems for ground and space applications, a thermoplate (heat sink). After the device is turned on, it may overheat abnormally during the process of reaching a stationary operating mode. Overheating is associated with the phenomenon of thermal load hysteresis during the onset of boiling, the transition from single-phase convection to developed boiling in the evaporator of a heat sink material. This work studied the influence of the construction parameters of thermoplate on the hysteresis phenomenon at the integral level. For this purpose, a thermoplate testing methodology was implemented, which includes experiments with slow (quasi-stationary) and quick heating after turning on the device immediately at full power. Overheating of the device is possible during both "slow" and "quick" heating. The maximum overheating in the experiments performed was ~18 K. Such overheating can pose a danger to the reliability of the device. The study was performed with ammonia as a coolant on 5 models of thermoplate that differ in evaporator channel roughness, length, material, longitudinal thermal conductivity, the heat capacity of the structure, etc. The danger of overheating the device is also determined by the maximum thermal load at which the device is operated. The following conclusions were made: the greatest influence on the hysteresis parameters is the value of the evaporator channel surface roughness. Increasing the roughness reduces the risk of overheating the device, and changes the nature of the "boiling curves" in the thermoplate; an increase in the length and longitudinal thermal conductivity has a favorable effect on reducing the risk of overheating; the evaporator surface is made of aluminum alloy instead of stainless steel, which makes hysteresis impossible; in the case of rapid heating of the thermoplate, the maximum heat flux at steady-state has an ambiguous effect: with its increase, overheating due to hysteresis first increases, and in the case of further increase, it decreases and may disappear altogether. A significant increase in the maximum heat flux compared to the heat flux at the beginning of boiling reduces the danger of hysteresis affecting the overheating of the device. The results of this work provide recommendations on how to avoid the dangerous overheating of the device due to the hysteresis phenomenon.

Lithological controls influence river form in contrasting sub‐catchments: The Scamander and Avenue Rivers, Tasmania

AbstractBedrock influence on river channel form is difficult to assess, with many catchments dominated by glacial erosion and with blanketing sediments from both pluvial and fluvial sources. The Scamander catchment in Tasmania lacks glacial history and features two bedrock‐confined sub‐catchments of similar area and maximum flow length, but one dominated by Mathinna Group sedimentary rocks, and the other with large areas in granite lithology. Lithology types, stream network parameters and near stream slope angles were analysed using geographical information systems, and results of stream cross sections, channel form and planforms were compared for each lithology. Results showed that granite features low gradient, shallow streams with channel slope cross sections of &lt;10°. Granite channels are irregular and dominated by large boulders that create channel roughness and resist incision. Weathering products of coarse quartz sand provide anchorages for in‐channel vegetation. By contrast, sedimentary Mathinna Group rocks feature steeply incised trough‐like channels, with near‐channel hillslope gradients mostly between 30° and 50°. Rectangular blocks disintegrate to gravel cobbles on the channel bed, providing poor anchorage for vegetation. Mathinna lithology influences steep, low roughness channels, and stable, incised recurved meanders formed by river interaction with vertical layers of resistant rock. The resistant bedrock lithology is demonstrated in this study to influence varied river planforms, near‐channel slope gradients, channel sediments and cross sections.

The effect of ice cover on velocity and shear stress in a riffle‐pool sequence

AbstractDischarge and channel geometry control velocity and bed shear stress within a reach. Channel roughness (e.g., riffles, pools) and ice cover in winter moderates velocity and shear stress at the bed. This study evaluated velocity profiles across a channel segment with variable bed roughness (e.g., riffles, pools) to determine changes in the position of maximum velocity, maximum velocity magnitude, and resulting bed shear stress estimates when ice cover was present. Using acoustic doppler velocimeter (ADV) and acoustic doppler current profiler (ADCP) high resolution velocity profiles were collected during ice cover, open water, and open water with significant increases in vegetation cover through a riffle‐pool sequence in a low‐order channel in southern Ontario Canada in the first half of 2021. Key findings were that in five of the seven cross‐sections, flow direction was significantly different when ice was present. Additionally, maximum velocities were closer to the bed during ice cover, a common finding in modelling and experimental work, and is confirmed in this field setting. Although maximum velocity magnitudes were not significantly different, derived bed shear stress values under ice were larger. Specifically, under ice conditions, riffle bed shear stress ranged 0–16 N/m2 compared to 0–9 N/m2 in ice free conditions. In the pool, bed shear stress ranged 0–6 N/m2 under ice cover, and 0–5 N/m2 in ice free conditions. Further, as flow levels increased through the spring and summer, this coincided with increased in‐stream vegetation cover, which decreased flow velocities near the bed, and thus decreased bed shear stresses to less than 1 N/m2 in both the riffle and pool sections. The findings indicate that channel evolution processes may be more intense during lower‐stage winter flows when ice is present and has significant implications for channel design, restoration and management strategies used in small channels impacted by ice cover.