Channel Velocity Research Articles

Two-stage attention Unet3d model under airfoil 3D turbulence field prediction with SDF expression

Various fluid mechanics software, due to inherent factors such as algorithms and boundary conditions, cannot quickly simulate 3D flow fields in batches, and the calculation of each model still takes a lot of time.In order to realize the rapid prediction of the three-dimensional flow field around the airfoil, this paper uses a new SDF geometric expression to describe the shape of the airfoil, and combines the prediction accuracy of the velocity and pressure channels, and proposes a two-stage Unet3d convolution prediction model based on the SDF expression, which greatly improves the prediction accuracy of the pressure channel.In addition, the introduced two-stage convolutional network is optimized by combining lightweight network and attention mechanism. On the premise of ensuring the accuracy of the network, it can effectively reduce the parameters of the network model and improve the operating efficiency of the network. The two-stage method was tested on the Naca0012 and RAE2822 three-dimensional datasets, and the average accuracy rates were 95.44% and 98.22% respectively, which were 2 to 3 percentage points higher than the original method.

Effectiveness of silver-magnesium oxide-water hybrid nanofluid in Couette channel

The present article numerically investigates the unsteady magnetohydrodynamic (MHD) Couette flow containing novel (Ag + MgO)-water hybrid nanofluid (HNF). The nanoparticles of silver (Ag) and magnesium oxide (MgO) are supplemented to base fluid water. The top wall is kept in uniform motion while the bottom wall of channel set stationary and stretchable. An external magnetic field is applied perpendicular to lower plate. The governed nonlinear partial differential equations (PDE) are solved employing finite difference method (FDM). The effects of hybrid nanofluid and nanofluid (NF) are compared for the significant parameters and presented graphically. The results illustrate that (Ag + MgO)-water HNF exhibits significant influence over Ag-water NF on velocity and temperature in the Couette channel.

The kinematic structure of magnetically aligned H i filaments

ABSTRACT We characterize the kinematic and magnetic properties of H i filaments located in a high Galactic latitude region (165° < α < 195° and 12° < δ < 24°). We extract three-dimensional filamentary structures using fil3d from the Galactic Arecibo L-Band Feed Array H i (GALFA-H i) survey 21-cm emission data. Our algorithm identifies coherent emission structures in neighbouring velocity channels. Based on the mean velocity, we identify a population of local and intermediate velocity cloud (IVC) filaments. We find the orientations of the local (but not the IVC) H i filaments are aligned with the magnetic field orientations inferred from Planck 353 GHz polarized dust emission. We analyse position–velocity diagrams of the velocity-coherent filaments, and find that only 15 per cent of filaments demonstrate significant major-axis velocity gradients with a median magnitude of 0.5 km s−1 pc−1, assuming a fiducial filament distance of 100 pc. We conclude that the typical diffuse H i filament does not exhibit a simple velocity gradient. The reported filament properties constrain future theoretical models of filament formation.

Impact of sediment size, channel velocity and plant density on sediment deposition inside Phragmites australis canopies

In this study, laboratory experiments were performed to investigate the impacts of sediment size, channel velocity and plant density on sediment deposition inside an emergent canopy constructed with Phragmites australis (P. australis) that included real plant morphology. Three sediment sizes (ds = 10, 22 and 48 μm), three plant densities (n = 0.006, 0.018 and 0.027 cm−2) and various mean channel velocities (U0 = 6 to 17 cm/s) were considered. Different mean channel velocities corresponded to the presence or absence of sediment resuspension in the bare channel, which led to distinct deposition patterns. Inside canopies, sediment deposition was dominated by the near-bed turbulent kinematic energy (near-bed TKE). At very low mean channel velocities (i.e., no resuspension in the bare channel), the pure deposition inside the canopy was the same as that in the bare channel. As the mean channel velocity increased but resuspension did not occur in the bare channel, the local vegetation-induced turbulence led to an increase in near-bed TKE within the canopy leading edge region, further causing the formation of a diminished deposition region. When the mean channel velocity was sufficiently large to produce resuspension in the bare channel, diminished and enhanced deposition regions were observed inside the canopy compared to the bare channel. A prediction method considering the impacts of sediment size, channel velocity, plant density and plant morphology was proposed to predict the length of the in-canopy diminished deposition region. The predictions and measurements were consistent. Different sediment sizes, channel velocities and plant densities led to two distinct sediment supply conditions inside the canopies. When sediment supply was not limited, finer sediment and/or sparser canopies led to longer diminished deposition regions, but the pure deposition inside the canopies remained constant. When sediment supply was limited, a different deposition pattern was observed. The pure deposition decreased along the canopy length, but the resuspension in the bare channel and canopy leading edge region might compensate for the limited sediment supply inside the canopy. A threshold representing the ratio of the advection time throughout the canopy to the particle settling time, κ, was defined to evaluate whether the sediment supply inside the canopy was limited. The sediment supply was not limited at κ < 0.4 but was limited at κ > 1.

Effect of Rigid Aquatic Bank Weeds on Flow Velocities and Bed Morphology

The prediction of changes in velocity distribution and channel bed morphology is significant in open channel management and design. This paper implements experimental work to realize and quantify the effect of rigid aquatic bank weeds on vertical velocity profiles and channel bed morphology. In the experimental work, weeds were given a staggered distribution using three distances of 25, 50, and 75 mm, unilaterally and bilaterally, with Froude numbers ranging from 0.11 to 0.30, achieving 168 scenarios. Results for the tested weed cases showed that the average velocity was directly proportional to the weed density and approached the Froude number. By comparing the smooth and weeded velocities, it was found that the velocity inside the infested reach was close to the downstream velocity and exceeded the upstream velocity by about 10% and 41%, respectively. Scour depths along the centerline of the vegetated reach for the bilateral weeds were higher by 11% to 33% than those for the unilateral weeds. The maximum observed depth of the scour holes along the smooth bank was about 30% to 60% of the maximum scour depth at the middle line. Finally, to quantify the results, multiple regression analysis was performed to develop empirical equations to assist in the water management process.

Performance study of a valveless piezoelectric pump with built-in semi-arc bluffbody antique tower channel.

According to the bluffbody bypass effect, the irregular bluffbody can be used to improve the valveless piezoelectric pump. This paper designs a semi-arc bluffbody based on the bluffbody bypassing principle to alleviate the phenomenon of fluid backflow. The fluid passes through the shape of the antique tower to further enhance pumping efficiency. A positive fluid flow mechanism in the pump cavity is theoretically derived. The simulation of the velocity and pressure distribution in the tower-shaped channel of the pump cavity leads to the conclusion that the forward flow has better performance than the reverse flow, and the correctness of the theory is also verified. Experiments further proved that the volume of fluid in the forward direction was reduced by 10.8% when compared to the reverse direction. The study of the height of different semi-arc bluffbody and the angle of the tower trough shows that as the height and angle increase, the flow rate grows first and then reduces. The maximum flow rate is 243.83 ml/min when the bluffbody height is 4mm and the channel angle is 20° (220V, 85Hz).

PERENCANAAN TEKNIS DRAINASE JALAN SAUDARA KOTA MEDAN

ABSTRACTJalan Saudara which is located in Medan Kota Subdistrict the city of Medan with the boundary between the Jalan SM Raja intersection and the Jalan Bahagia intersection with a length of 743 m is very prone to flooding, especially during the rainy season. The dimensions of the drainage channels are small and vary between open and closed channels. Drainage problems on your road a) The area of the inundation area is 1000 meters, b) The width of the inundation area is 6 m, c) The inundation height is 20 cm, d) Inundation duration is 15 minutes, e) Inundation frequency is every heavy rain and f) The causes of flooding are due to the dimensions of the canal small and there is a blockage of several damaged culverts. The aim of the research is to design the dimensions of the drainage channels along Jalan Saudara so that they can accommodate all water waste activities and are expected to overcome flooding in the area. The methodology is carried out by analyzing hydraulics and hydrological analysis to determine the calculation of maximum rainfall, rainfall intensity, time of concentration and discharge of runoff, flow velocity in drainage channels, design of channel discharge, and design of channels. The calculation results obtained a) The intensity of maximum rainfall with the analysis of various methods, it was found that the Log Pearson III method was the best used. This was done by statistical tests with chi-square and with Smirnov-Kolmogorov, b) The detailed design of the drainage using precast concrete in the form of a closed U-Ditch with dimensions of 120 cm x 100 cm with a height varying between 120 cm and 160 cm. c) At a certain point, drainage using Box culverts with dimensions of 150 cm x 100 cm with a height of 150 cm.Kewords: Saudara Street, Drainage, Technical Planning

Phasic icing phenomena of part single cells during the successful cold start processes of PEMFC stacks

Herein, phasic icing of part single cells during successful cold start process of PEMFC stacks is experimentally studied considering temperature, gas velocity and cell number; meanwhile, a heat transfer model is developed for stacks to investigate thermal evolution characteristics. The results reveal that temperature difference between end cells and middle cells can be 10 °C, and that for a cell inside may reach 7 °C. For self-starts, no apparent icing phenomenon is observed when PEM stack is successfully started at ≥ −20 °C. Phasic icing occurs commonly at ≤ −30 °C and performance degradation due to icing is less than 0.5%. In a 20-cell stack, when cathode gas channel velocity is 6.2 m/s, phasic icing in middle cells is observed due to uneven flow distribution, which can be avoided by increasing the velocity to 12.4 m/s if velocity is 3.1 m/s or less, cold start fails. Additionally, coolant circuit cannot eliminate endplate effect and phasic icing phenomenon.

Investigation of the flow and heat transfer performance of supercritical pressure hydrocarbon fuel in a novel rotating internal trapezoidal expansion channel

Hydrocarbon fuel is required to cool the rotating turbine blades in order to enable the hypersonic vehicle electricity supply turbine to withstand the impact of hot air. A novel internal trapezoidal expansion type hydrocarbon fuel rotating cooling channel is proposed for heat transfer enhancement of turbine blades. Numerical results show that among the expansion channels studied, the maximum value of thermal performance is obtained for the expansion angle 2° channel. The thermal performance of the channel corresponding to the expansion angle of 2° is maximally increased by 591.4% compared to the 0° channel. The factor of friction of the channel corresponding to the expansion angle of 2° is lowered maximally by 99.7% compared to the 0° channel. The channel thermal performance of the entrance temperature before the temperature of the critical state is improved by a maximum of 911.3% compared to the channel thermal performance of the entrance temperature after the temperature of the critical state. The internal trapezoidal expansion channels overcome the negative effect of the second channel velocity decrease caused by the increase in physical property of the fuel due to centrifugal force, and significantly enhance the second channel heat exchange capacity.

Designing a device for measuring the velocity of liquid flowing in open channels

Water flow systems in open channels are designed according to certain levels. Flow rate increases in open channels can bring many disasters. Therefore, it is necessary to routinely measure flow in open channels. In addition to rivers and streams, open channels are used in many areas in city life. If open channels are not checked regularly, floods may occur in sudden rains and human life may be endangered. Practical problems like measurement, control and linearization of mechanical outputs can be solved within the context of function generation problem. In this work, an exemplary design associated with the measurement of water velocities in open channels and the resulting apparatus has been shown. To test its performance, velocities have been compared with those obtained by the constructed prototype. The results have been observed to be consistent with each other.

A fractional model of magnetohydrodynamics Oldroyd-B fluid with couple stresses, heat and mass transfer: A comparison among Non-Newtonian fluid models

The present article aims to extend some of the already existing fluid models to a large class of fluids namely, “Oldroyd-B couple stress fluid (OBCSF)”. The main focus of the present work is to combine the existing fluid models in ordered to get a new class of fluid. The unsteady magnetohydrodynamics (MHD) Oldroyd-B fluid (OBF) with couple stresses, porosity, heat and mass transfer is considered in the present analysis. The Oldroyd-B couple stress fluid is assumed to flow in channel. The classical model is fractionalized by considering Atangana-Baleanu (AB) operator in ordered to highlight the memory analysis. To develop closed form solutions the combined (Laplace + Fourier) integrals have been used. The results obtained are portrayed through graphs for all pertinent flow parameters which involved in the present dynamic model. Moreover, the impact of AB time fractional parameter is investigated graphically on flow, temperature and concentration distributions exploiting MATHCAD software. Secondly, for better understanding the present solutions of Oldroyd-B couple stress fluid (OBCSF) are reduced to Odroyd-B fluid (OBF) without couple stresses, Maxwell solutions, Couple stress solutions and Newtonian viscous fluid solutions and the results have been compared for classical and fractional order derivatives. In addition to this a limiting case is carried out by our solutions to already published work which verify our solutions. In addition to this during the analysis we noticed that the flow heat and concentrated get lowered for the escalating numerical values of AB fractional derivatives. Similarly, it is also noticed that the velocity in channel accelerated with the increment of numeric values of pressure, porosity, thermal buoyancy and relaxation time parameter. In the same manner temperature and concertation profiles gets low with the higher values of Prandtl number, Reynold number and fractional operator. Finally, skin friction for momentum equation, Nusselt number for temperature and Sherwood number for concentration have been calculated and given in tabular forms.

Nature of striation in 21 cm channel Maps: velocity caustics

ABSTRACT The alignment of striated intensity structures in thin neutral hydrogen (H i) spectroscopic channels with Galactic magnetic fields has been observed. However, the origin and nature of these striations are still debatable. Some studies suggest that the striations result solely from real cold-density filaments without considering the role of turbulent velocity fields in shaping the channel’s intensity distribution. To determine the relative contribution of density and velocity in forming the striations in channel maps, we analyse synthetic observations of channel maps obtained from realistic magnetized multiphase H i simulations with thermal broadening included. We vary the thickness of the channel maps and apply the Velocity Decomposition Algorithm to separate the velocity and density contributions. In parallel, we analyse GALFA-H i observations and compare the results. Our analysis shows that the thin channels are dominated by velocity contribution, and velocity caustics mainly generate the H i striations. We show that velocity caustics can cause a correlation between unsharp-masked H i structures and far-infrared emission. We demonstrate that the linear H i fibers revealed by the Rolling Hough Transform (RHT) in thin velocity channels originate from velocity caustics. As the thickness of channel maps increases, the relative contribution of density fluctuations in channel maps increases and more RHT-detected fibers tend to be perpendicular to the magnetic field. Conversely, the alignment with the magnetic field is the most prominent in thin channels. We conclude that similar to the velocity channel gradients (VChGs) approach, RHT traces magnetic fields through the analysis of velocity caustics in thin channel maps.

Holistic Cloud-AI Fusion for Autonomous Conversational Commerce in High-Velocity E-Commerce Channels

Given the pace at which e-commerce is growing, high velocity channels require synchronous, individual, and highly engaging methods of dealing with the customers. In this research, the combination of cloud computing and AI is proposed and an organization conversational commerce framework will be created to enhance digital economies flexibility and autonomy. Taking advantage of cloud-AI synergy, the presented system improves efficiency, computing, and customer interaction through constructive architectural structures and sophisticated algorithms. This research assesses the potential of the proposed framework in improving the overall performance and the level of customer interaction of e-commerce transactions through comparing its efficiency in improving response time and enhancing user satisfaction metrics using a case study approach. The study concludes that moving towards the integration of cloud and AI both facilitates scalability while at the same time improves resource utilization and withstands fluctuating e-commerce conversational systems. Finally, this paper provides suggestions for e-commerce firms interested in implementing such cloud-AI solutions, with a focus on the areas of concern and future research directions.

Predicting flow velocity in a vegetative alluvial channel using standalone and hybrid machine learning techniques

The presence of vegetation in the water bodies has a profound effect on the flow velocity in an open channel due to the resistance offered by it. In rivers, estuaries, and coastal locations, vegetation significantly impacts the local hydrodynamics, which in turn affects various morphodynamic and biophysical processes. In this context, an accurate prediction of flow velocity in a vegetative alluvial channel is paramount. Several empirical and data-driven methodologies have been proposed as viable solutions in the literature to predict the flow velocity in a vegetative alluvial channel. Empirical equations cannot always be trusted to be accurate, but they have the advantage of being simple and physically appealing. Since machine learning (ML) techniques can capture complicated non-linear correlations, they are frequently employed to map natural processes. In this work, we investigate the performance of multiple standalone and hybrid Machine Learning (ML) techniques for predicting flow velocity (U) in a vegetative alluvial channel. An array of datasets available in the literature, comprising wide ranges of the number of cylinders per unit horizontal area (m), flow depth (h), channel slope (i), height of the vegetation (k), diameter of cylindrical vegetation (D), and non-dimensional drag coefficient (Cd) have been utilized in this study. For standalone methods, we made use of the M5Prime and Random Tree (RT) methods, while for hybrid ML method approaches, we made use of the Additive Regressor (AR) and Bagging (BA) methods. In the present study, six ML methods, viz., M5P, AR-M5P, BA-M5P, RT, BA-RT, and AR-RT, have been explored and their performance has also been analyzed. Among the proposed methods, AR-M5P provides the highest prediction (R2 = 0.954, CC = 0.977, NSE = 0.954, MAE = 0.042, MSE = 0.003, and Pbias = 1.466), followed by BA-M5P, BA-RT, M5P, RT, and AR-RT for the prediction of flow velocity in a vegetative alluvial channel. We have also performed the sensitivity analysis and found that the height of vegetation is the most sensitive variable in flow velocity prediction.

Experimental and Computational Investigation of Shaped Film Cooling Holes Designed to Minimize Inlet Separation

Abstract Film cooling is used to protect turbine components from the extreme temperatures by ejecting coolant through arrays of holes to create an air buffer from the hot combustion gases. Limitations in traditional machining meant film cooling holes universally have sharp inlets, which create separation regions at the hole entrance. The present study uses experimental and computational data to show that these inlet separation are a major cause of performance variation in crossflow fed film cooling holes. Three-hole designs were experimentally tested by independently varying the coolant velocity ratio (VR) and the coolant channel velocity ratio (VRc) to isolate the effects of crossflow on hole performance. Leveraging additive manufacturing (AM) technologies, the addition of a 0.25D radius fillet to the inlet of a 7-7-7 shaped hole is shown to significantly improve diffuser usage and significantly reduce variation in performance with VRc. A second AM design used a very large radius of curvature inlet to reduce biasing caused by the inlet crossflow. Experiments showed that this “swept” hole design did minimize biasing of the coolant flow to one side of the shaped hole, and it significantly reduced variations due to varying VRc. RANS simulations at six VR and three VRc conditions were made for each geometry to better understand how the new geometries changed the velocity field within the hole. The sharp and rounded inlets were seen to have very similar tangential velocity fields and jet biasing. Both AM inlets created more uniform, slower velocity fields entering the diffuser. The results of this article indicate that large improvements in film cooling performance can be found by leveraging AM technology.

Evaluation of spacer-induced hydrodynamic mixing using particle image velocimetry: Impact on membrane distillation performance

Net-type spacers are used to promote hydrodynamic mixing in the feed channel of crossflow membrane filtration. The induced fluid flow mitigates concentration and temperature polarization effects on the membrane surface, leading to the enhancement of heat/mass transfer across the membrane. The objective of this research is to study the effect of spacer geometry on fluid flow and heat/mass transfer in the feed channel. The particle image velocimetry (PIV) technique was used to measure flow velocity in the feed channel with net-type spacers. Flow characteristics at a wide range of Reynolds numbers were described in terms of time-averaged mean velocity and turbulence kinetic energy (TKE). The PIV result revealed distinct profiles of mean velocity and TKE at different channel heights with bi-planar spacers. The spacer with the largest hydrodynamic angle of 120° (Net120) was found to be the most efficient in promoting flow unsteadiness because it led to the largest channel-averaged TKE among the selected spacers. The unsteady flow regime on Net120 was accompanied by the greatest pressure drop over the feed channel. Moreover, the effect of spacer-induced mixing on heat/mass transfer across the membrane was further evaluated via the flux measurement with vacuum membrane distillation experiments. In comparison with other spacers, Net120 resulted in a relatively higher flux because of the improved hydrodynamic mixing. These findings reveal the validity of the experimental approach in identifying the impact of key spacer design parameters on hydrodynamic mixing. Nusselt number was calculated to relate the hydrodynamic flow and thermal flow in the feed channel of membrane distillation, and a modified Nusselt number correlation was proposed to better predict convective heat transfer in the spacer-filled channel in VMD.

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.

Numerical and experimental study on the hydrodynamic characteristics of the hub vortex at the nozzle of a water jet propulsion pump unit

The generation and development of hub vortices in the wake of water jet propulsion pump units lead to energy loss and reductions in propulsion efficiency and hydrodynamic performance. In this study, a numerical scheme is developed to simulate the internal and external flow fields of water jet propulsion pump units, and visual experiments are used to verify the numerical results. The hub vortices are observed to develop from the vortex structure at the tail edge of the guide vane and vortex clusters on both sides of the guide cone tip. The vortex structure at the tail edge of the guide vane is generated by the pressure gradient in this region. As the axial distance increases, this structure gradually becomes concentrated around the hub vortex position and vorticity loss occurs. The radius of the hub vortex gradually increases with increasing axial distance at the nozzle section. The rotational speed of the periphery of the hub vortex progressively affects the flow velocity in the nozzle channel.

Geoacoustic Inversion with a Single Vector Sensor and Multichannel Dispersion Curves

This paper discusses the value added by using a single vector sensor over a conventional pressure-only hydrophone for geoacoustic inversions. Inversion methods based on genetic algorithms are used to estimate the seabed properties. Synthetic signals of impulsive arrivals first are modeled using KRAKEN and RAM propagation models, each being modified to predict components of the vector field. While KRAKEN is utilized to directly compute dispersion curves, RAM provides full-field results that require the application of time warping to separate the modal arrivals. Combinations of dispersion curves utilizing all vector sensor channels are compared to curves estimated with the pressure-only channel. Within the time warping analysis, both binary masking and band-pass filter masking methods are applied to compare stability of results. The environment modeled for the synthetic analysis and inversion method utilize sound speed profiles measured during the Monterey Bay 2019 at-sea experiment and assume a sediment layer of constant thickness overlying a deeper sub-bottom type. White noise is added to the synthetic data at different signal-to-noise ratios to evaluate the impact of signal excess on the results. A hybrid optimization approach is used to improve the results of the genetic algorithm method. The analysis with synthetic data is consistent with the analysis of broadband, impulsive data collected from the experiment, indicating that the additional information from the vertical velocity channel further improves the geoacoustic parameter estimates.

Highly structured turbulence in high-mass star formation: An evolved infrared-dark cloud G35.20-0.74 N

Context. Massive stars are generally believed to form in environments characterized by supersonic turbulence. However, recent observations challenge this traditional view. High-spatial- and spectral-resolution observations of the Orion Molecular Cloud (OMC, the closest massive star formation region) and an infrared-dark cloud (IRDC) G35.39 (a typical distant massive star formation region) show a resolution-dependent turbulence, and that high-mass stars are forming exclusively in subsonic to transonic cores in those clouds. These studies demand a re-evaluation of the role of turbulence in massive star formation. Aims. We aim to study the turbulence in a typical massive-star-forming region G35.20-0.74 N (G35.20 in short) with sufficient spatial resolution to resolve the thermal Jeans length, and sufficient spectral resolution to resolve the thermal line width. Methods. We use the Atacama Large Millimeter/submillimeter Array (ALMA) dust continuum emission to resolve fragmentation, the Karl G. Jansky Very Large Array (JVLA) 1.2 cm continuum to trace ionized gas, and JVLA NH3 (1,1) to (7,7) inversion transition lines to trace line width, temperature, and dynamics. We fit those lines and remove line broadening due to channel width, thermal pressure, and velocity gradient to obtain a clean map of intrinsic turbulence. Results. We find that (1) the turbulence in G35.20 is overall supersonic, with mean and median Mach numbers 3.7 and 2.8, respectively. (2) Mach number decreases from 6–7 at a 0.1 pc scale to less than 3 toward the central cores at a 0.01 pc scale. (3) The central ALMA cores appear to be decoupled from the host filament, which is made evident by an opposite velocity gradient and significantly reduced turbulence. Because of intense star-formation activity in G35.20 (as compared to the relatively young and quiescent IRDC G35.39), the supersonic turbulence is likely replenished by protostellar outflows. G35.20 is therefore representative of an evolved form of IRDC G35.39. More observations of a sample of IRDCs are highly demanded in order to further investigate the role of turbulence in the initial conditions required for massive-star formation.