Turbulence Intensity Research Articles

Response and Reliability Analysis of Concrete Chimneys under Random Vortex Shedding

Vortex-induced forces on chimneys can be modelled as a random process described by its power spectral density and cross-power density functions. The response of the chimney to such forces, including aeroelastic interaction, is of significant interest to researchers. In this paper, the response and reliability analysis of chimneys under random vortex-induced excitation is given, in which aeroelastic interaction is duly considered. Both modal and direct spectral analyses are presented, using discrete modelling of the chimney. The reliability of the chimney against the vortex-induced forces is determined using Vanmarck’s double barrier crossing analysis. The effects of the important parameters such as the turbulence intensity, lift coefficient, correlation length, Strouhal number, and total damping on the response and reliability estimate of three chimneys are investigated. The responses of the chimneys obtained by the international wind codes are compared with those determined from the random vibration analysis and the reasons for differences in responses are reported. The novelty of this paper is the response and reliability analysis of the chimney, including aeroelastic interaction, under random vortex shedding forces using the discrete formulation, and to study the effect of important parameters on the responses of chimney.

The effects of absorptive capacity on competitive intelligence in a turbulent market

ABSTRACT The business environment of small and medium-sized enterprises’ (SMEs) is becoming increasingly unstable and unpredictable because of fierce competition and a turbulent marketplace. This study examines the role of absorptive capacity as an antecedent of competitive intelligence and assesses the moderating effects of market turbulence and competitive intensity in this relationship. Data were collected from 140 manufacturing firms in Quebec and analysed by using partial least squares structural equation modelling (PLS-SEM). The results reveal that absorptive capacity positively influences competitive intelligence; moreover, market turbulence and competitive intensity are conditional factors that affect competitive intelligence activity. Directions for future research and managerial implications are further discussed.

Impacts of Changing Atmospheric Circulation Patterns on Aviation Turbulence Over Europe

AbstractAddressing aviation turbulence not only enhances passenger comfort but also help to reduce fuel consumption and environmental impact, supporting aviation sustainability. By using ERA5 reanalysis data we explore how changing atmospheric circulation, monitored via sea level pressure trends, impacts aviation turbulence over Europe. Our results show coherent climate anomalies, with rising turbulence intensity over the UK and Northern Europe where most events involve clear air turbulence, which occurs unexpectedly and without warning, particularly at flight altitudes. We also highlight a clear seasonal patterns in moderate‐or‐greater turbulence encounters, most frequent and intense in winter, with a key role of wind shears due to the sub‐tropical jet position over Southern Mediterranean. Our approach adds to previous studies on the same topic by analyzing individual atmospheric circulation pattern changes and their effects on turbulence‐related factors. This offers insight into how climate change affecting atmospheric dynamics may contribute to increased aviation turbulence.

Influence of freestream turbulence and porosity on porous disk-generated wakes

This study aims to evaluate the effect of freestream turbulence (FST) on wakes produced by disks with different porosity. The wakes are exposed to various freestream turbulence “flavors,” where turbulence intensity and integral length scale are independently varied. The turbulent wakes are interrogated through hot-wire anemometry from 3 to 15 diameters downstream of the disks. It is found that disks with low porosity behave similarly to a solid body, in terms of both entrainment behavior and scaling laws for the centerline mean velocity evolution. Far from the disks, the presence of FST reduces both the wake growth rate and entrainment rate, with a clear effect of both turbulence intensity and integral length scale. As porosity increases, these “solid body” FST effects gradually diminish and are reversed above a critical porosity. The entrainment behavior in disk-generated wakes is significantly influenced by the presence of large-scale coherent structures, which act as a shield between the wake and the surrounding flow, thus impeding mixing in the near wake. We found that higher porosity, turbulence intensity, or integral length scale weakens the energy content of these structures, thereby limiting their influence on wake development to a shorter distance downstream of the disk. This, in turn, potentially reduces the influence of large-scale engulfment on the overall entrainment mechanism to a shorter distance downstream of the disks as well. For low-porosity disks, freestream turbulence intensity initially promotes near-wake growth through the suppression of large-scale structures; however, farther downstream, the wakes grow faster when the background is nonturbulent. Published by the American Physical Society 2024

EFFECTS OF LOCALIZED NON-GAUSSIAN ROUGHNESS ON HIGH PRESSURE TURBINE AERO-THERMAL PERFORMANCE: CONVECTIVE HEAT TRANSFER, SKIN-FRICTION AND THE REYNOLDS' ANALOGY

Abstract Compressible direct numerical simulations are conducted to investigate how surface roughness affects the aero-thermal performance of a high pressure turbine vane operating at an exit Reynolds number of 0.59 × 106 and exit Mach number of 0.92. The roughness under investigation here was synthesized with non- Gaussian statistical properties and an amplitude that varies over its chord length — representative of what truly occurs on an in-service vane. Particular attention is directed towards how sys- tematically changing the axial extent of leading edge roughness affects convective heat transfer (Nusselt and Stanton numbers) and aerodynamic drag (skin-friction coefficient) on the pressure and suction surfaces. The results of this investigation demonstrate that moving the larger amplitude roughness further along the suc- tion surface can cause major changes in the blade boundary-layer state. In fact, towards the trailing-edge of one of the rough vanes investigated here, the local skin-friction coefficient increases by a factor of twenty-three (2, 300%) compared to smooth-vane lev- els, whereas the local Stanton number increases by a factor six (600%). The disproportionate rise of drag compared to heat transfer is explored in further detail by quantifying the Reynolds' analogy and by calculating the fractional contributions of pres- sure drag and viscous drag to the total drag force. The effect of varying the inlet turbulence intensity and integral length-scale for a fixed roughness topography is also investigated, along with the Reynolds-number scaling of heat transfer and drag.

Patterns of lean methane-air mixtures combustion in piston engine

The article is devoted to the study of the patterns of combustion of lean methaneair mixtures in marine internal combustion engine. Literature review shows that the implementation of combustion technology for a homogeneous lean methaneair mixture will increase the compression ratio, reduce fuel consumption and improve the environmental engine performance. However due to an increase in misfires and a decrease in the speed of flame propagation, the combustion of lean methaneair mixtures remains an unresolved problem. The article studies the influence of the excess air coefficient (from 1 to 1.4) on the turbulent combustion regime (assessed by the Karlowitz and Damkoehler criteria), the completeness and rate of fuel combustion. It was revealed that depletion of the air fuel mixture under conditions of intense turbulence leads to an increase in the Karlowitz criterion and a decrease in the Damköhler criterion. This indicates that the rate of chemical reactions in the flame front decreases, as a result of which the combustion process is characterized by stretching and rupture of the flame front. Therefore, to intensify the combustion of lean methaneair mixtures, it is advisable to increase the average speed of the vortex flow, and not the intensity of turbulence. A study of the influence of the excess air coefficient on the completeness and rate of fuel combustion showed that depletion of the mixture leads to a decrease in the completeness of fuel combustion from 93.5 % (at α=1) to 83 % (at α=1.4). The combustion rates also decrease and their maximum values shift from 13° (at α=1) to 24° (at α=1.4) degrees after top dead center. Therefore for efficient engine operation on lean mixtures, it is necessary to increase the fuel combustion rate through additional swirling of the gasair mixture or the use of combustion promoters.

Effect of pulsation intensity on flow and dispersion characteristics of single-pulsed dual parallel plane jets

The effect of pulsation intensity on flow and dispersion characteristics of single-pulsed dual parallel plane jets was experimentally investigated in this study. A single jet from a pair of dual jets was pulsed by a loudspeaker. The flow evolution processes were examined using the laser-light sheet-assisted smoke flow visualization method. The visual spread of the jet flow was measured using the binary boundary edge detection technique. A hotwire anemometer was used to detect the instantaneous velocities, mean velocities, turbulence intensities, Lagrangian integral time, and length scales. The dispersion capabilities of the jet fluid were evaluated employing the tracer-gas concentration detection technique. Two characteristic flow modes, namely the coherent vortices and vortex breakup, could be classified based on pulsation intensity. At Ip < 1.0, the flow was characterized by coherent vortices, which maintained coherence within one excitation cycle. At Ip > 1.0, vortex breakup occurred, where vortices deformed, lost coherence, and transformed into puff-shaped vortical structures within one excitation cycle. The vortices emerging from the pulsed jet undergo deformation, evolving into puff-shaped vortices, and subsequently fragment into smaller turbulent eddies more quickly than the synchronized vortices from the non-pulsed jet. This leads to significant penetration and velocity fluctuations in the trajectory of the pulsed jet. Consequently, the overall spread width and concentration reduction index of the single-pulsed dual parallel plane jets exceed those of the non-pulsed dual parallel plane jets.

A LES-ALM Study for the Turbulence Characteristics of Wind Turbine Wake Under Different Roughness Lengths

To investigate the characteristics of wind turbine wakes under different aerodynamic roughness lengths, a series of LES-ALM simulations were carried out in this study. First, a sensitivity analysis of the time step of the simulation results was performed. Then, the study compared the power and thrust of wind turbines under different roughness conditions. Finally, the mean velocity deficit, added turbulence intensity, and Reynolds shear stresses in the wake were analyzed under different roughness conditions. This study finds that a 0.1 s time step can provide satisfactory results for the LES-ALM compared to a 0.02 s time step. Furthermore, for the same hub-height wind speed, the thrust coefficient varies from 0.75 to 0.8 under the different roughness levels. As the roughness length increases, the time-averaged velocity deficit and added turbulence intensity decreases, and the wake recovers more quickly at the incoming level. However, the effect of roughness length on the Reynolds shear stress is weak within the downstream range of x = 6D to 10D. For the velocity deficit, a single Gaussian function is not able to describe its vertical distribution. Additionally, under higher roughness conditions, the height of the wake center is distinctively higher than the hub height as the wake develops downstream. The findings of this paper are beneficial for selecting the approximate numerical parameters for the wake simulations and provide deeper insights into the turbulence mechanisms of wind turbine wake, which are crucial for establishing analytical models to predict the wake field.

Wind loads on square lattice towers with tubular members based on wind tunnel test and numerical simulation

The square lattice tower with tubular members (SLTTM) is widely used in civil engineering. Wind load is the primary factor affecting the stability of these structures. This paper presents the wind loads of the SLTTM at different Reynolds numbers (Re) through wind tunnel testing and large eddy simulation (LES). A series of wind tunnel tests with four segment models were first conducted to discuss the effects of wind direction, turbulence intensity, and solidity ratio on the aerodynamic force under low and subcritical Reynolds numbers. The LES method was subsequently employed to determine the aerodynamic force coefficient at Re = 191–1.34 × 106 in both the smooth and uniform turbulent wind fields. The results from wind tunnel tests indicate that the mean and fluctuating drag coefficients at low Reynolds numbers are somewhat different from those at subcritical Reynolds numbers. The solidity ratio and wind direction exert a notable influence on the mean drag coefficient, whereas their impact on the fluctuating drag coefficient is relatively minimal. As the turbulence intensity increases, both the mean and fluctuating drag coefficients exhibit a notable rise. The results of the LES at Re = 191–1.34 × 106 show that an increase in turbulence intensity can markedly elevate the fluctuating drag coefficient. However, the effect on the mean drag coefficient is found to depend on the Reynolds number range. The Reynolds number effect on the mean and fluctuating drag coefficients of the SLTTM may be primarily attributed to the members without and with a shielding effect, respectively.

Experimental Study of Turbulent Premixed Flames of Gas-to-Liquids (GTL) Fuel in a Fan-Stirred Combustion Bomb

This study experimentally investigates the turbulent flame speeds (St) of Gas-to-Liquids (GTL) fuel and a 50/50 blend with diesel across turbulence intensities (u') ranging from 0.5 to 3.0 m/s and equivalence ratios (Φ) from 0.7 to 1.3. Experiments were conducted using a cylindrical fan-stirred combustion bomb at an initial temperature (Ti) of 463 K and atmospheric pressure under near homogeneous and isotropic turbulence (HIT) conditions. A pressure transducer measured the St of the propagating GTL flame. High-speed imaging reveals that changes in flame brightness are associated with variations in flame temperature and soot incandescence. Compared to diesel, stoichiometric GTL and the 50/50 diesel-GTL blend showed peak combustion pressure reductions of 8.9% and 4.9%, respectively. Rich diesel fuel and lean GTL exhibited higher pressure rise rates, flame propagation, and St due to their Lewis numbers (Le) being less than one, enhancing flame-turbulence interaction. At u` of 0.5, 1.5, and 3.0 m/s, St for GTL increased by approximately 3.6%, 5.3%, and 2.8%, respectively, when compared to diesel, with these increases observed at Φ < 1.1. Transition from wrinkled to corrugated flamelets with increasing u` supports models predicting flame stability and potential industrial combustion efficiency improvements. Comparisons with numerical St results using the Zimont Turbulent Flame Speed Closure (Zimont TFC) model showed good agreement at lower (u' = 0.5 m/s) and mid-range (u' = 2.0 m/s) turbulence intensities but discrepancies at higher intensities (u' = 3.0 m/s), highlighting the need to refine numerical models for more accurate predictions across all turbulence levels.

Large-scale turbulence effects on flow dynamics around and aerodynamic forces on a square cylinder

Turbulence effects on the aerodynamics of a square cylinder have been widely investigated due to their fundamental significance in both flow physics and engineering applications. However, the influence of large-scale turbulence on shear layer unsteadiness, and its consequences on flow structure and aerodynamic forces has received insufficient attention. The present study explores these effects, considering turbulent flows with turbulence intensities up to 20% and integral length scales up to four times the characteristic length of the obstacle. A reduced-order model and measurable indicators of flow dynamics are employed to investigate the underlying mechanisms quantitively. The findings reveal that large-scale, high-intensity freestream turbulence amplifies the root mean square (rms) flapping amplitudes of shear layers by provoking and superposing a set of low-frequency unsteadiness with energy levels comparable to that of Karman vortex shedding. The alteration in shear layer behavior results in (1) an extended region of high rms pressures around the square cylinder and (2) intermittent shear layer reattachment, followed by an intermittent weakening of the vortex shedding. These effects lead to a significant increase in rms pressure coefficients on the lateral and leeward surfaces, as well as an intermittent suppression of lift forces. Two new flow patterns were observed during periods of weakened flow dynamics: (1) vortices forming above the lateral surfaces shed downstream directly without interacting with the shear layer on the other side; and (2) Karman vortices in the wake region break down before shedding downstream.

Experimental investigation of the flow disturbance near the trailing edge of slotted and non-slotted blades using skewness and kurtosis

The present study conducts an experimental investigation into the flow characteristics over a cascade of both slotted and non-slotted compressor blades. The focus is on evaluating potential statistical correlations between higher-order moments of velocity fluctuations, including Skewness and Kurtosis. The linear axial cascade comprises three NACA6409 blades, which are tested in both normal and slotted blade. Data acquisition was conducted using a hot wire anemometer at three measurement stations within the cascade. The hot wire sensor was positioned at distances of x/c = 0.125, 0.25, and 0.5 from the trailing edge (x), where x represents the distance from the probe to the trailing edge of the airfoil and (c) is the chord length of the blade. Measurements were taken at a blade angle of attack of 0° and two Reynolds numbers: 22,750 and 45,500. Results indicate that blade grooving enhances flow velocity, postpones separation and improves flow control in the trailing edge region. By comparing calculated Skewness and Kurtosis values with those predicted by existing boundary layer and free jet relations, more consistent correlations were identified. To provide more accurate relationships, two polynomials of the second and third order have been used. It was found that high-order values of velocity were obtained more accurately with the relations presented in this research. Although the accuracy of these predictions is significantly reduced in the proportion of larger distances. In distant stations, the loss velocity has decreased. As the distance from the model increases, the amount of inhomogeneities in the sequence increases and the values of the opposite Skewness become zero. Turbulence intensity has been reduced by slotting the blades.

Flow measurement in a wind tunnel with blockage screens

The small and medium-scale wind turbine development have been improved due to their adaptability in offshore and onshore localities for wind farm applications. Blockage effects caused by numerous impediments restrict the flow-field near the turbine and impact the turbine's performance. The testing and optimization of turbines in such conditions at laboratory-level are challenging due to the unavailability of customized wind tunnel configurations with blockage screens. The present work focuses on the design, development and evaluating aerodynamic performance of wind tunnel with and without blockage screens. A comprehensive design is established by evaluating losses in each section, uncertainties, velocity, forces, and turbulence intensity in the wind tunnel through the experimental analysis. The novel blockage screens are arranged to maintain 5% and 10% blockage percentage for wind velocity range of 2 to 14 m/s. The maximum velocity reduction with 5% blockage is 41.40% and this drop reaches to 67.84% for 10% blockage. Consequently, available wind power is seen to undergo a maximum reduction of 79.88% and 96.67%, respectively.

Computational Study on Flow Characteristics of Shocked Light Backward-Triangular Bubbles in Polyatomic Gas

This study computationally examined the Richtmyer–Meshkov instability (RMI) evolution in a helium backward-triangular bubble immersed in monatomic argon, diatomic nitrogen, and polyatomic methane under planar shock wave interactions. Using high-fidelity numerical simulations based on the compressible Navier–Fourier equations based on the Boltzmann–Curtiss kinetic framework and simulated via a modal discontinuous Galerkin scheme, we analyze the complex interplay of shock-bubble dynamics. Key findings reveal distinct thermal non-equilibrium effects, vorticity generation, enstrophy evolution, kinetic energy dissipation, and interface deformation across gases. Methane, with its molecular complexity and higher viscosity, exhibits the highest levels of vorticity production, enstrophy, and kinetic energy, leading to pronounced Kelvin–Helmholtz instabilities and enhanced mixing. Conversely, argon, due to its simpler atomic structure, shows weaker deformation and mixing. Thermal non-equilibrium effects, quantified by the Rayleigh–Onsager dissipation function, are most significant in methane, indicating delayed energy relaxation and intense turbulence. This study highlights the pivotal role of molecular properties, specific heat ratio, and bulk viscosity in shaping RMI dynamics in polyatomic gases, offering insights on uses such as high-speed aerodynamics, inertial confinement fusion, and supersonic mixing.

Hydrodynamic analysis of fish swimming behavior in turbulent river confluences

This study focuses on selecting the most appropriate turbulence model for simulating fish swimming behavior in river confluences. To achieve this, three numerical models—k-ε, k-ω, and large eddy simulation—were compared by running simulations under identical flow conditions and evaluating the results against biological experimental data. Among the models, the k-ω model demonstrated the smallest relative error, consistently within 5% of the experimental results, confirming its superior accuracy and reliability for this application. The k-ω model's ability to capture boundary layer turbulence and near-wall flow dynamics proved essential for studying fish swimming in complex turbulent environments. Simulations revealed that both the flow velocity ratio between the main stream and tributary and the confluence angle are critical factors influencing the flow structure. At higher flow velocity ratios (R = 1/3 and 3/1) or large confluence angles (α ≥ 90°), turbulence intensity increased, leading to more complex vortex formations that significantly impacted fish swimming speed. When the flow velocity ratio (R) is 1/3, the fish can achieve a maximum swimming speed of 2.75 L/s, which is significantly higher than the swimming speed of 1.18 L/s observed when R is 3/1. Additionally, fish closer to the center of the flow field experienced greater turbulence, resulting in higher energy expenditure. The findings provide crucial insights into the hydrodynamic mechanisms driving fish swimming behavior in dynamic aquatic environments.

Axial-flow-induced structural vibration in a 5×5 cylinder cluster

This work aims to experimentally study the incident turbulence intensity Tu effect on the flow-induced vibration of an elastic cylinder positioned at the center of a 9- or 25-cylinder cluster subjected to an axial flow. Tu is examined at 0.71% – 0.80% and 2.30% – 2.91%. The pitch-to-diameter ratio P* is 1.36 ∼ 1.64. Lateral vibrations along two orthogonal directions are simultaneously measured with the interstitial flow of the cylinder bundle. Two mechanisms are identified behind the elastic-cylinder vibration at low and high Tu. One is the presence of a varying velocity gradient within the cylinder bundle, and the other is incident flow fluctuations. At low Tu (0.71% – 0.80%), the root-mean-square vibration amplitude Arms* of the elastic cylinder exhibits strong dependence on the P* and cylinder number N. Increasing velocity gradient with decreasing P* or increasing N plays a key role in destabilizing the shear layers surrounding the elastic cylinder, inducing eddies to separate from the cylinder-wall and actively interact with those near the neighboring cylinder. Therefore, the near-wall velocity fluctuation urms* and Arms* are increased. At high Tu (2.3% – 2.91%), Arms* is weakly dependent on P* compared with that at low Tu. It is found that the shear-layer instability surrounding the elastic cylinder is mainly intensified by the incident flow fluctuations with a higher Tu, accounting for the enhanced eddy activities, while the velocity-gradient effect associated with a change in P* is of less importance.

Experimental study on aeration characteristics of plunging wave impact on a vertical cylinder

The impact force exerted by plunging breakers on structures is most pronounced, with the impact pressure being most sensitive to the changes in air entrainment, posing a threat to the structural safety of offshore wind turbines. However, the current explanations of the high impact force mechanisms in plunging waves are relatively superficial, and the relationship between the air entrainment motion and pressure oscillations remains unclear. According to the experimentally obtained pressure characteristics and the formation of entrapped air, this paper systematically divides the process of plunging wave impact on a vertical cylinder into three stages: breaking wave crest impact, entrained air cavity impact, and plume impact. Employing a bubble image velocimetry platform to visualize flow field characteristics and quantify turbulence intensity, we investigated the connection between gas motion and impact loads. The results indicate that the conversion of gas energy is closely related to the load characteristics, with the maximum impact force occurring near the peak of the energy gradient. The gas movement significantly influences pressure oscillations, which are positively correlated with the gas's physical compression and expansion characteristics. This study has uncovered new insights into the phenomenon of plunging waves impacting wind turbine towers and has enhanced the understanding of its load characteristics.

Near wake evolution of a tidal stream turbine due to asymmetric sheared turbulent inflow with different integral length scales

Tidal stream turbines deployed at highly energetic open water sites are subjected to sheared inflow in the rotor plane. The inflow shear is expected to cause asymmetric loading on the rotor blades and affect the downstream wake. In the current study, two different turbulent inflow conditions, static-high shear and dynamic shear, were generated via an active-grid turbulence generator. A 1:20 scaled three-bladed horizontal axis tidal turbine model was tested in those conditions. The results were compared to a quasi-laminar case with no imposed turbulence or shear. The results show that the high shear reduces the average performance, with a drop of up to 16% in the optimal power coefficient. Besides, the shear profiles increase torque fluctuations and induce significant differences in wake hydrodynamics between the high-speed (upper) and low-speed (lower) regions. The large integral length scales further enhance the load fluctuations perceived by the rotor but have a negligible effect on the mean wake field quantities. The wake recovery was found to be ∼2 to 4 times faster in the upper half region than in the lower region in the near wake. The lower half region featured a faster breakdown of tip vortex structure and a rapid drop of swirl number, a phenomenon conjectured to be a consequence of the strong turbulence intensities and Reynolds stresses in the lower half region. The sheared turbulent inflow also results in a very intensive energy redistribution process towards large-scale, low-frequency motions, which is important to the downstream turbines.

U-Turn Shape Effect on Effective Thermal Conductivity of Double Pass Photovoltaic Thermal (PVT) Systems Configuration

This study explores the thermal performance of double-pass photovoltaic thermal (PVT) systems by investigating the influence of turn shape on heat transfer characteristics using computational fluid dynamics (CFD) simulations. The aim is to evaluate various turn shapes, including half-circle, triangle, half-hexagon, half-octagon, and box, to determine their impact on turbulent intensity, effective thermal conductivity, and outlet temperature in PVT systems. The investigation reveals significant variations in heat transfer efficiency among the different turn shapes, with the triangle-shaped turn demonstrating superior performance across multiple parameters. The findings highlight that the triangle-shaped turn exhibits enhanced turbulence generation and heat exchange efficiency compared to other shapes. Specifically, the triangle-shaped turn achieves a maximum turbulent intensity of approximately 70%, surpassing other shapes which achieve around 60%. Moreover, the triangle-shaped turn displays a longer and more substantial area of high heat exchange, resulting in an effective thermal conductivity improvement of up to 20% compared to alternative shapes. Furthermore, the analysis indicates that the triangle-shaped turn exhibits a faster increase in outlet temperature, reaching steady-state conditions within 15 seconds, while other shapes require up to 19 seconds. These results underscore the significance of turn shape in optimizing the thermal efficiency of PVT systems.

The Influence of Non-Pressure Pipes Filled to Different Degrees on the Hydraulic Characteristics of Channel–Pipe Combined Irrigation Systems

Modern irrigation areas often use a combination of channels and pipes for irrigation. Due to changes in terrain, inflow, and pipe diameter, pipelines are often prone to experiencing a state of no pressure. This lack of pressure affects not only the velocity distribution and water surface profile of the main channel but also the velocity distribution and flow distribution of the pipeline. Therefore, in this study, we employed a combination of physical model experiments and theoretical analysis to study the influence of non-pressure pipelines on the hydraulic characteristics of channel–pipe combined irrigation systems filled to different degrees. Through this, the variation laws of the flow velocity distribution, turbulence intensity, water surface, diversion width, and diversion ratio under different filling degrees were obtained. The non-pressure pipeline flow velocity expression was obtained through dimensional analysis, and the calculation formula for the non-pressure pipeline flow velocity coefficient was fitted using linear regression analysis. The relative error between the calculated value and the measured value did not exceed 8.81%. The research results presented in this article can provide technical support for the design and maintenance of channel–pipe combined irrigation systems.