Main Flow Patterns Research Articles

Numerical Study on Gas Blown in Tundish Side Walls

The performance of gas blown in side walls of a single strand tundish is numerically simulated. Three cases are studied, i.e. tundish without gas blown, tundish with gas blown from the right side wall, and from the front wall. The vortex circulating flow is the main flow structure in tundish without gas blown. The gas blown from the right side wall of tundish will significantly change the flow field. The short-circuit flow that the tracer flow along the bottom of tundish to the outlet is becoming the main flow pattern. The RTD curve shows a rapid increase tendency. An anticlockwise flow near the top surface is formed. The mixing of tracer in the tundish is delayed and the dead volume fraction is increased when compared with the tundish without gas blown case. In contrast, the gas blown from the front wall of tundish will divide the tundish into two parts. The strong circulation flow in two parts is formed. Besides, the mixing of tracer is faster and the dead volume fraction is lower than that of the case without gas blown. This case may be an optimized gas blown technology in tundish.

Dimensionless Analysis of the Effects of Junction Angle on the Gas-Liquid Two-Phase Flow Transition and the Scaling Law of the Microbubble Generation Characteristics in Y-Junctions

Gas-liquid two-phase flow patterns and gas slug hydrodynamics were experimentally studied in three Y-junctions with different junction angles of 60°, 90° and 120°. Microbubbles were generated in the sodium alginate aqueous solution with the surfactant Tween20. Four main flow patterns were observed, i.e., stratified flow, annular flow, dispersed bubble flow and slug bubble flow. The formation mechanism of the bubble flow was explained by a force analysis, which was based on the dimensionless analysis regarding Capillary number, Weber number and Euler number. The transition criteria of the gas-liquid two-phase flow patterns was set up by these three dimensionless numbers. Additionally, the characteristics of the slug bubble were investigated, which made a scaling criterion for eliminating the influence of the angle factor become possible. A new scaling law (validity range within 2.88 < Re1 < 14.38, 0.0068 < We1 < 0.1723) was proposed to predict the bubble size and it showed a good agreement with the experimental results.

Numerical study of thermal fluid dynamics and solidification characteristics during continuous wave and pulsed wave laser welding

Pulsed wave (PW) mode laser welding is often preferred under conditions where specific heat input and tailorable cooling rate are required. Previous works on numerical modelling of laser welding mainly focus on continuous wave (CW) mode, while physical understanding of PW mode from numerical investigation is scarce. In this work, a 3D multi-physics thermal fluid model is developed considering both CW and PW modes laser welding. The main physical factors involving heat transfer, thermal fluid flow, Fresnel absorption, recoil pressure induced by metal evaporation, Marangoni effect driven by surface tension, free surface tracing, and laser multiple reflections inside the keyhole are included in this model. The model is tested and validated against the corresponding experimental results for laser welds of stainless steel 316 L. The simulated weld fusion cross sections and surface molten pool agree well with the experimentally observed results for both CW and PW modes. The results show that PW mode exhibits a higher depth of penetration and a smaller molten pool at the same heat input with CW mode. In CW mode laser welding, the shape of keyhole is unstable, while its depth keeps relatively stable. There are two main flow patterns in the molten pool of CW mode welding: an outward flow from keyhole outlet to the rear weld pool and a clockwise flow from the keyhole tip to the rear weld pool. While for PW mode, keyhole and molten pool show periodic behaviors with a period of the laser energy output used. The periodic fluid flow pattern is mainly affected by the gradually changed surface tension and suddenly changed recoil pressure. Furthermore, it is found that a finer microstructure with a smaller secondary dendrite arm spacing is obtained in PW mode due to a higher cooling rate from both the calculated and experimentally measured results.

Probabilistic identification of Preferential Groundwater Networks

We characterize key features of subsurface flow paths relying on an energetic and probabilistic perspective. We consider subsurface flow in a free aquifer system as mainly ruled by gravity, the latter acting as the key driving force. Therefore, we study groundwater circulation relying upon stochastic simulations of aquifer bottom topography inferred from stratigraphic observations. Upon resting on the concept of optimal channel networks, we identify Preferential Groundwater Networks (PGNs) as spatially organized structures carved by locally following the steepest gradient associated with the aquifer bottom topography. A probabilistic description of PGNs is obtained by reconstructing the aquifer bottom topography as a spatial random field conditional on the available information, and using diverse area threshold values for PGNs delineation. We find that PGNs inferred from the (ensemble) averaged bottom topography with the highest area threshold considered are strikingly consistent with main flow directions and key subsurface flow patterns inferred from available piezometric data. The probabilistic distribution of PGNs is also consistent with geological and hydrogeological information at our disposal, such as geological data (and ensuing hydrogeological sections), and is coherent with the nature of the aquifers investigated.

Dimensionless Artificial Intelligence-Based Model for Multiphase Flow Pattern Recognition in Horizontal Pipe

Summary Multiphase flow analysis attracts a lot of attention from researchers from diverse disciplines. There are several studies including experimental, theoretical modeling, and numerical analysis that were carried out to investigate the multiphase flow. However, many facets of multiphase flow are still unresolved owing to the extremely complex nature of the multiphase flow. The complex interactions of the different phases are leading to different flow regimes that are difficult to predict but essential for developing the computational model. The identification of the flow pattern is still a challenging task. One of the growing fields is the machine learning approach, which can address such complex problems. This study aims to use machine learning to develop models that can identify the flow patterns in multiphase flow. To achieve the objective, a large set of experimental data was collected. The effect of fluid properties, such as density, viscosity, and surface tension, on the flow pattern was introduced by changing the fluid properties. The wide range of data was processed by applying a machine learning technique for predicting the flow regimes. The models were built using dimensionless parameters to extend their validity for various design and operational conditions. This approach enables to capture the main flow pattern as well as subcategories of flow patterns in the horizontal pipe. Comparison and analyses of the different machine learning tools were carried out to investigate classification of multiphase flow patterns. The results showed that different artificial intelligence (AI) methods can predict the flow pattern in horizontal pipes with high accuracy. The results of using Reynold’s number for liquid (ReL) and gas (ReG) as an input to predict the flow patterns are deficient in accuracy for the support vector machine (SVM) and discriminant analysis (DA). However, the prediction capability of the model was improved by introducing Weber’s number for liquid (WeL) and gas (WeG) along with the Reynolds numbers (ReL and ReG). The improvement in the flow pattern prediction owing to the introduction of Weber’s number is speculated because of the capturing hydrodynamic phenomenon (inertia and surface tension) owing to change in fluid properties. It infers that capturing hydrodynamic phenomena affecting the flow pattern and their transition is essential for the prediction of flow patterns in multiphase flow.

Gas-liquid vertical pipe flow patterns convolutional neural network classification using experimental advanced wire mesh sensor images

Flow pattern identification for simultaneous gas-liquid flow in pipes is a central problem in the petroleum industry. However, there are many conventional methods used for flow patterns identification that come with some form of restrictions limited to specific operating conditions. Although previous studies made efforts to make flow patterns identification free from biases (subjectivity), objective predictions are yet to be fully explored. For the first time, this study employs a 4-layer convolutional neural network (CNN) architecture and threshold segmentation algorithm to classify industrial working fluids of air/silicone oil flow patterns in a vertical pipe. Also, an advanced wire mesh sensor (WMS) instrumentation was used to obtain the cross-sectional frame images from a series of 52 experimental runs. This study made an attempt to use the sequential cross-sectional frames original data obtained from the experimental WMS because it is the crossing wires of the WMS that interact with the flow field and also capture the main flow pattern transitional zones. The obtained experimental testing results indicate that the supervised CNN model has an accuracy of 99.90% better than the seven-benchmarked supervised machine learning classification models used in recognizing bubbly, slug and churn flow patterns. The CNN model experimental test accuracy also outwits other related flow patterns identified in the literature when compared, thereby affirming the model's robustness. Since the WMS provide high spatial and temporal resolutions data, the average pixel intensity values from the segmented images were used as the flow indicator in identifying the transition zones within the main flow patterns. Furthermore, the Locally Interpretable Model-agnostic Explanation (LIME) algorithm for the first time was used to explain and interpret features in the WMS flow images that were contributing to the overall CNN classification scores. Finally, the CNN trained model was able to classify the main flow patterns and segmented transitional zones with certainty and confidence without subjectivity which is inherent in the direct conventional methods.

Comparison of the influence of 2D and 3D geometry of the main chamber on plasma parameters in the SOL of ASDEX Upgrade

In this paper the influence of toroidally asymmetric wall features on plasma solutions for ASDEX Upgrade is investigated by using the 3D scrape-off-layer simulation code EMC3-EIRENE. A comparison of simulation results in a 2D case with a toroidally symmetric first wall and divertor and a 3D case that differs from the 2D setup by including the 3D structure of the poloidal rib-limiters on the low field side of ASDEX Upgrade, highlights notable differences in the main chamber neutral particle distributions, ionisation sources and plasma flow patterns. Both neutral particle distribution and ionisation sources extend poloidally further upwards at the outer mid-plane in the 3D case and the plasma flow is globally influenced by the 3D wall features. Both simulations are conducted with identical input parameters to isolate the influence of wall geometry from other factors. By analysing the transport of neutrals from different poloidal locations it was possible to explain the observed discrepancies by different transport paths for recycled neutrals from the divertor region, only accessible in the 3D version of the wall geometry. Together with observed differences in fall-off lengths for plasma flow and electron temperature at the outer mid-plane, presented results are of key importance for interpreting global impurity migration experiments.

Numerical Investigation of Flow Characteristics of Molten Steel in the Tundish with Channel Induction Heating

In the continuous process, fluid flow is an important physical phenomena in the tundish, as it affects the process of heat transfer, bubble motion and inclusion collision-coalescence and grow up. This paper undertakes a detailed numerical investigation of fluid flow characteristics in the tundish with and without induction heating. The individual unit method and the volume subtraction model are applied to analyze the flow characteristics. A quantitative evaluation method of flow characteristics is proposed to investigate the flow characteristics. In the tundish with and without induction heating, firstly, the main flow behavior of molten steel is mixed flow in the receiving chamber; secondly, the main flow behavior of molten steel is plug flow in the channel; lastly, the main flow pattern is mixed flow, and the minor flow pattern is plug flow in the discharging chamber. The method of the volume subtraction model is an effective way to analyze the flow characteristics in the tundish with channel induction heating.

CFD modelling of the isobaric evaporation of cryogenic liquids in storage tanks

A new CFD model relevant to isobaric cryogen evaporation and weathering in storage tanks has been developed. It treats the heat influx from the surroundings into the vapour and liquid phases separately and allows for heat transfer between the two phases. The model accurately predicts the dynamics of the vapour flow and the vapour to liquid heat transfer. It provides well-resolved velocity and temperature profiles in the vapour phase, as well as evaporation and boil-off gas rates. It demonstrates that the main flow pattern is that the vapour circulates upwards close to the tank wall, then radially along the roof towards the tank axis, where the flow is partitioned; between a fluid that leaves the tank, and a fluid that recirculates back towards the vapour bulk. The results of simulations, carried out in different sized tanks with different initial amounts of cryogen, were compared with the results of the Huerta and Vesovic non-equilibrium model. The results indicate that, for the purposes of modelling heat transfer between the phases, steady-state vapour temperature and boil-off gas rate, the complex flow established in the vapour phase can be adequately modelled by the effective advective, upward flow from the interface.

Flow Pattern Map of Flow Boiling in a Rectangular Channel Filled with Porous Media

A flow visualization study was carried out for flow boiling in a rectangular channel filled with and without metallic random porous media. Four main flow patterns are observed as intermittent slug-churn flow, churn-annular flow, annular-mist flow, and mist flow regimes. These flow patterns are clearly classified based on the high-speed images of the channel flow. The results of the flow pattern map according to the mass flow rate were presented using saturation temperatures and the materials of porous media as variables. As the saturation temperatures increased, the annular-mist flow regime occupied a larger area than the lower saturation temperatures condition. Therefore, the churn flow regime is narrower, and the slug flow more quickly turns to annular flow with the increasing vapor quality. The pattern map is not significantly affected by the materials of porous media.

An Additively Manufactured Four-Sensor Fast Response Aerodynamic Probe

Abstract This study describes the design, development, and testing of a miniature fast response aerodynamic probe (FRAP) with four sensors (4S), which are able to perform measurements in the unsteady three-dimensional flow field. Moreover, the calibration and first results with the newly developed probe are provided. The miniature FRAP-4S demonstrates a 3 mm tip diameter, offering a 25% reduction in diameter size, in comparison to a first-generation FRAP-4S, without any loss in terms of measurement bandwidth. The 3 mm outer casing of the probe is additively manufactured with a high-precision binder jetting technique. In terms of aerodynamic performance, the probe demonstrates high angular sensitivity up to ± 18 deg incidence angle in both directions. To evaluate the measurement accuracy of the newly developed FRAP-4S, measurements are performed at the Laboratory for Energy Conversion (LEC) in both a round axisymmetric jet and an one-and-a-half stage, unshrouded and highly loaded axial turbine configuration. Turbulence measurements performed with the miniature FRAP-4S are compared against hot-wire studies in round free-jets found in the literature. Good agreement in both trends but also absolute values is demonstrated. Moreover, the performance of the probe is compared against traditional instrumentation developed at LEC, namely, miniature pneumatic and FRAP-2S probes. The results indicate that the FRAP-4S, despite its larger size in comparison to the other probes tested, can resolve the main flow patterns, with the highest deviations occuring in the presence of highly skewed and sheared flow. Furthermore, the additively manufactured probe was proven to be robust after more than 50 hours of testing in the representative turbine environment configuration. Finally, it should be highlighted that the newly developed FRAP reduces measurement time by a factor of three in comparison to FRAP-2S, which directly translates to reduced development time and thus cost during the turbomachinery development phase.

Passage of a rising bubble through a liquid‐liquid interface: A flow map for different regimes

AbstractThe passage of a rising air bubble through a stratified horizontal interface between two Newtonian liquids is studied numerically. A ternary phase‐field model has been utilized for capturing the interface between three immiscible fluids. According to the previous studies, the density, viscosity, and surface tension of the two liquids, in addition to the bubble diameter, are the effective parameters of bubble interaction with the interface. By changing these variables, three main flow patterns are identified in numerical simulations. Penetration flow regime is observed when the bubble enters the upper liquid alone and does not raise the lower liquid. Entrainment flow regime occurs when the bubble lifts some of the heavier liquid to the lighter liquid but still rises alone. If the bubble holds a film of the denser liquid when it rises in the upper liquid, envelopment flow regime takes place. A flow regime map is represented to distinguish the aforementioned flow patterns using Weber and Morton numbers and determine regime transition criteria based on these two dimensionless parameters. For Weber numbers lower than 30, or Morton numbers higher than 1.7 × 10−2, the penetration regime is observed. On the contrary, when the Weber number is higher than 65 and the Morton number is lower than 7 × 10−5, the envelopment regime occurs. The entrainment pattern happens between these ranges and two additional limiting relations of 320Mo0.18 < We < 1500Mo0.23.

Hydrodynamics and gas-liquid mass transfer of CO2 absorption into [NH2e-mim][BF4]-MEA mixture in a monolith channel

This is the first work to investigate the hydrodynamics and gas-liquid mass transfer of carbon dioxide (CO2) absorbed into the amino-functionalized ionic liquid (IL) [NH2e-mim][BF4] and monoethanol-amine (MEA) mixture through a vertical circular monolith channel by means of computational fluid dynamics (CFD). It is shown that there are five flow patterns (i.e., bubbly flow, Taylor flow, slug-bubbly flow, slug-annular flow, and annular flow), and Taylor flow is the main flow pattern. The intrinsic kinetics of CO2 absorbed into the [NH2e-mim][BF4]-MEA mixture was obtained, the reaction orders relative to CO2, [NH2e-mim][BF4], and MEA being 1, and the activation energy Ea (19,313 and 28,991 J•mol−1) and pre-exponential factor k0 (3.34×105 and 7.04×106 mol-1•L•min−1) for CO2 absorbed in [NH2e-mim][BF4] and MEA were derived. After the kinetic parameters were imported into the mass transfer model, it was found that the liquid phase volumetric mass transfer coefficient (kLa) in the presence of a chemical reaction can be improved by three to eight times, indicating that mass transfer can be enhanced remarkably by chemical reaction. Moreover, a correlation formula is developed to predict kLa, which agrees well with the simulation results. This work provides a new way to capture CO2 with the combination of IL and MEA in a monolith reactor.

3D-printed, patient-specific intracranial aneurysm models: From clinical data to flow experiments with endovascular devices.

Flow models of intracranial aneurysms (IAs) can be used to test new and existing endovascular treatments with flow modulation devices (FMDs). Additionally, 4D flow magnetic resonance imaging (MRI) offers the ability to measure hemodynamics. This way, the effect of FMDs can be determined noninvasively and compared to patient data. Here, we describe a cost-effective method for producing flow models to test the efficiency of FMDs with 4D flow MRI. The models were based on human radiological data (internal carotid and basilar arteries) and printed in 3D with stereolithography. The models were printed with three different printing layers (25, 50, and 100µm thickness). To evaluate the models in vitro, 3D rotational angiography, time-of-flight MRI, and 4D flow MRI were employed. The flow and geometry of one model were compared with in vivo data. Two FMDs (FMD1 and FMD2) were deployed into two different IA models, and the effect on the flow was estimated by 4D flow MRI. Models printed with different layer thicknesses exhibited similar flow and little geometric variation. The mean spatial difference between the vessel geometry measured in vivo and in vitro was 0.7±1.1mm. The main flow features, such as vortices in the IAs, were reproduced. The velocities in the aneurysms were similar in vivo and in vitro (mean velocity magnitude: 5.4±7.6 and 7.7±8.6cm/s, maximum velocity magnitude: 72.5 and 55.1cm/s). By deploying FMDs, the mean velocity was reduced in the IAs (from 8.3±10 to 4.3±9.32cm/s for FMD1 and 9.9±12.1 to 2.1±5.6cm/s for FMD2). The presented method allows to produce neurovascular models in approx. 15 to 30h. The resulting models were found to be geometrically accurate, reproducing the main flow patterns, and suitable for implanting FMDs as well as 4D flow MRI.

Prediction and management of hydrate reformation risk in pipelines during offshore gas hydrate development by depressurization

The hydrate reformation in marine gas hydrate production system can significantly affect the accuracy control of the production pressure differential and even cause pipeline blockage problems. In this paper, a transient temperature and pressure calculating model was established to predict the risk of hydrate reformation in production pipelines during offshore gas hydrate development, which considering the coupling interactions between the real-time drainage of electric submersible pump (ESP), the downhole preheating of electric induction heater (EIH), the wellbore multiphase flow and heat transfer. Using the model, the dynamic evolution laws of gas–liquid two-phase flow behaviors in different pipelines of mixed transportation, drainage and gas production were studied. Furthermore, the region of hydrate reformation in production pipelines was predicted quantitatively. The results indicate the risk of hydrate reformation in the drainage pipe is the highest relative to other pipes, and the main flow pattern in this pipe is bubbly flow. Besides, the conventional hydrate management method through inhibitor injection was applied to prevent the hydrate reformation. It can be found that the required Ethylene glycol (MEG) minimum concentration reaches 22% in order to completely eliminate the risk of hydrate reformation. To this end, a new hydrate management strategy by adding additional pumps and heaters was proposed, and the prevention effect of hydrate reformation in different scenarios was discussed in detail. The simulated results demonstrate that this method can effectively address the potential hydrate reformation risks without the use of inhibitors. This work will provide theoretical references for the hydrate flow assurance operations in marine gas hydrate production testing.

Longitudinal shear stress response in human endothelial cells to atheroprone and atheroprotective conditions

The two main blood flow patterns, namely, pulsatile shear (PS) prevalent in straight segments of arteries and oscillatory shear (OS) observed at branch points, are associated with atheroprotective (healthy) and atheroprone (unhealthy) vascular phenotypes, respectively. The effects of blood flow-induced shear stress on endothelial cells (ECs) and vascular health have generally been studied using human umbilical vein endothelial cells (HUVECs). While there are a few studies comparing the differential roles of PS and OS across different types of ECs at a single time point, there is a paucity of studies comparing the temporal responses between different EC types. In the current study, we measured OS and PS transcriptomic responses in human aortic endothelial cells (HAECs) over 24 h and compared these temporal responses of HAECs with our previous findings on HUVECs. The measurements were made at 1, 4, and 24 h in order to capture the responses at early, mid, and late time points after shearing. The results indicate that the responses of HAECs and HUVECs are qualitatively similar for endothelial function-relevant genes and several important pathways with a few exceptions, thus demonstrating that HUVECs can be used as a model to investigate the effects of shear on arterial ECs, with consideration of the differences. Our findings show that HAECs exhibit an earlier response or faster kinetics as compared to HUVECs. The comparative analysis of HAECs and HUVECs presented here offers insights into the mechanisms of common and disparate shear stress responses across these two major endothelial cell types.

Numerical analysis of electrohydrodynamic flows of a dielectric liquid in a wire–plate configuration with cross Poiseuille flow

A numerical investigation of electrohydrodynamic flows of a dielectric liquid in a single wire–plate configuration with a cross Poiseuille flow has been presented. Unipolar charge injection takes place from a metallic wire electrode immersed in a dielectric liquid at the center of the channel. Although this configuration is frequently studied with gas as a working fluid in electrostatic precipitators, the flow of a dielectric liquid remains unexplored. Two-way coupled governing equations that include the Navier–Stokes equations for fluid flow, the charge transport equation, and the Poisson equation for electric potential are solved using a finite-volume method. A systematic analysis of flow characteristics with respect to the hydrodynamic Reynolds number (Re) and electric Reynolds number (RE) has been carried out. The transition process with four distinct flow patterns and two different flow mechanisms are discussed in detail. A comprehensive map of flow patterns with respect to various dimensionless parameters has been proposed. The results show that a higher Re can reduce the effect of electric field, and vice versa. The main flow pattern is found to be a strong function of the dimensionless external velocity.

Recognition of two-phase flow pattern inside evaporator tubes

The convective heat exchange mechanism in two-phase regime, can allow high exchange coefficients, as long as particular conditions are respected, in terms of vapor quality. In evaporator tubes this problem is particularly important as a deviation from the optimal flow conditions can drastically drop the efficiency of the heat exchange. This work describes an innovative methodology for identifying the different two-phase flow regimes in evaporator pipes, through the processing of the vibrational data acquired on the pipe itself. An experimental apparatus with transparent pipes has been built up to recognize flow patterns by a fast image acquisition camera. Images have been associated to vibration data acquired on pipes by accelerometer. The analysis of frequency spectrum, led to first interesting results thus it is possible to distinguish between “no bubbles” regimes and different “bubbles” regimes. A wide test campaign has been realized on vertical and horizontal pipes, simulating steam bubbles with nitrogen bubbles, reproducing the main flow patterns. The paper demonstrates the possibility to design smart and non-intrusive sensor to be applied on evaporated tubes for the recognizing of anomalous thermal flow condition and sets the stage for future engineering work.

A Simple Conceptual Model for the Heat Induced Circulation over Northern South America and Meso-America

The physical description of the atmosphere’s general circulation over Northern South America and Meso-America deserves a more comprehensive explanation. This work presents the Pacific coast of Colombia as the rainiest place on Earth, with annual rainfall averaging 5000 to 13,000 mm, and record values as high as 13,159 mm for the location of Puerto López (77∘14′ W, 2∘50′ N). Using information from the ECMWF ERA-40 Atlas and ERA-Interim Reanalysis, we describe the existence of a concentrated diabatic heating source due to condensation and the main features of its related circulation over Northern South America and Meso-America. For simplicity, we used the analytical solution of the Phlips-Gill Model to diagnose the main flow patterns. Results show that the diabatic source over western Colombia generates equatorial trapped Rossby-Kelvin waves, which dominate the low-level circulation. A Kelvin wave explains the low-level easterly flows over the Tropical Atlantic Ocean, the Caribbean Sea, the Venezuelan-Colombian Llanos, and the Northern Amazon Basin. This circulation is analogous to a Walker cell. To the west, two cyclonic flows and strong westerly winds are present in Meso-America and the far eastern Pacific because planetary waves propagate there. A slight asymmetry in the equator’s diabatic heating location is responsible for the intense low-level pressure over Panama. The vertical velocity over the source area induces vortex tube stretching, and zonal mean flow excites a mixed wave and a northward flow.

Slope Erosion and Hydraulics during Thawing of the Sand-Covered Loess Plateau

Seasonal freeze-thaw processes have led to severe soil erosion globally. Slopes are particularly susceptible to changes in runoff, it can be useful to study soil erosion mechanisms. We conducted meltwater flow laboratory experiments to quantify the temporal and spatial distribution of hydraulic parameters on sandy slopes in relation to runoff and sediment yield under constant flow, different soil conditions (unfrozen slope: US; frozen slope: FS), and variable sand thickness. The results showed that sand can prolong initial runoff time, and US and FS have significantly different initial runoff times. There was a significant linear relationship between the cumulative runoff and the cumulative sediment yield. Additionally, hydrodynamic parameters of US and FS varied with time and spatially, as the distance between US and FS is linearly related to the top of the slope. We found that the main runoff flow pattern was composed of laminar flow and supercritical flow. There was a significant linear relationship between flow velocity and hydraulic parameters. The flow velocity is the best hydraulic parameter to simulate the trend of slope erosion process. This study can provide a scientific basis for a model of slope erosion during thawing for the Loess Plateau.