Effects of Biochar Addition on Rill Flow Resistance

The development of rills on a hillslope whose soil is amended by biochar remains a topic to be developed. A theoretical rill flow resistance equation, obtained by the integration of a power velocity distribution, was assessed using available measurements at plot scale with a biochar added soil. The biochar was incorporated and mixed with the arable soil using a biochar content BC of 6 and 12 kg m−2. The developed analysis demonstrated that an accurate estimate of the velocity profile parameter Гv can be obtained by the proposed power equation using an exponent e of the Reynolds number which decreases for increasing BC values. This result pointed out that the increase of biochar content dumps flow turbulence. The agreement between the measured friction factor values and those calculated by the proposed flow resistance equation, with Гv values estimated by the power equation calibrated on the available measurements, is characterized by errors which are always less than or equal to ±10% and less than or equal to ±3% for 75.0% of cases. In conclusion, the available measurements and the developed analysis allowed for (i) the calibration of the relationship between Гv, the bed slope, the flow Froude number, and the Reynolds number, (ii) the assessment of the influence of biochar content on flow resistance and, (iii) stating that the theoretical flow resistance equation gives an accurate estimate of the Darcy–Weisbach friction factor for rill flows on biochar added soils.

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Rill flow resistance law under sediment transport

Journal of Soils and Sediments ◽

10.1007/s11368-021-03083-x ◽

2021 ◽

Author(s):

Costanza Di Stefano ◽

Alessio Nicosia ◽

Vincenzo Palmeri ◽

Vincenzo Pampalone ◽

Vito Ferro

Keyword(s):

Sediment Transport ◽

Flow Velocity ◽

Friction Factor ◽

Flow Resistance ◽

Fixed Bed ◽

Accurate Estimate ◽

Mean Flow ◽

Mobile Bed ◽

Resistance Equation ◽

Rill Flow

Abstract Purpose In this paper, a deduced flow resistance equation for open-channel flow was tested using measurements carried out in mobile bed rills with sediment-laden flows and fixed bed rills. The main aims were to (i) assess the effect of sediment transport on rill flow resistance, and (ii) test the slope-flow velocity relationship in fixed bed rills. Methods The following analysis was developed: (i) a relationship between the Γ function of the velocity profile, the rill slope and the Froude number was calibrated using measurements carried out on fixed bed rills; (ii) the component of Darcy-Weisbach friction factor due to sediment transport was deduced using the corresponding measurements carried out on mobile bed rills (grain resistance and sediment transport) and the values estimated by flow resistance equation (grain resistance) for fixed bed rills in the same slope and hydraulic conditions; (iii) the Γ function relationship was calibrated using measurements carried out on mobile bed rills and the data of Jiang et al. (2018). Results This analysis demonstrated that the effect of sediment transport on rill flow resistance law is appreciable only for 7.7% of the examined cases and that the theoretical approach allows for an accurate estimate of the Darcy-Weisbach friction factor. Furthermore, for both fixed and mobile beds, the mean flow velocity was independent of channel slope, as suggested by Govers (1992) for mobile bed rills. Conclusions The investigation highlighted that the effect of sediment transport on rill flow resistance is almost negligible for most of the cases and that the experimental procedure for fixing rills caused the unexpected slope independence of flow velocity.

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Heat transfer performance and friction factor of various nanofluids in a double-tube counter flow heat exchanger

Thermal Science ◽

10.2298/tsci200323280z ◽

2020 ◽

Vol 24 (6 Part A) ◽

pp. 3601-3612

Author(s):

Dan Zheng ◽

Jin Wang ◽

Yu Pang ◽

Zhanxiu Chen ◽

Bengt Sunden

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Heat Exchanger ◽

Friction Factor ◽

Flow Resistance ◽

Heat Transfer Performance ◽

Weight Fraction ◽

Transfer Performance ◽

Tube Heat Exchanger ◽

High Heat Transfer

Experimental research was conducted to reveal the effects of nanofluids on heat transfer performance in a double-tube heat exchanger. With nanoparticle weight fraction of 0.5-2.0% and Reynolds number of 4500-14500, the flow resistance and heat transfer were analyzed by using six nanofluids, i.e., CuO-water, Al2O3-water, Fe3O4-water, ZnO-water, SiC-water, SiO2-water nanofluids. Results show that SiC-water nanofluid with a weight concentration of 1.5% provides the best improvement of heat transfer performance. 1.0% CuO-water and 0.5% SiO2-water nanofluids have lower friction factors in the range of Reynolds number from 4500-14500 compared to the other nanofluids. Based on test results of heat transfer performance and flow resistance, the 1.0% CuO-water nanofluid shows a great advantage due to a relatively high heat transfer performance and a low friction factor. Finally, empirical formulae of Nusselt numbers for various nanofluids were established based on experimental data tested in the double-tube heat exchanger.

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Slope threshold in rill flow resistance

10.5194/egusphere-egu21-10212 ◽

2021 ◽

Author(s):

Alessio Nicosia ◽

Vito Ferro

Keyword(s):

Friction Factor ◽

Flow Resistance ◽

Sediment Load ◽

Steep Slope ◽

Limiting Factor ◽

Rill Erosion ◽

Hydraulic Characteristics ◽

Transport Capacity ◽

Steep Slopes ◽

Rill Flow

Rills are small, steep sloping and ephemeral channels, shaped in soils, in which shallow flows move. Rill erosion strictly depends on hydraulic characteristics of the rill flow and for this reason flow discharge Q, rill width w, water depth h, mean flow velocity V, and friction factor are required to model the rill erosion process.Erosive phenomena strictly depend on the attitude of the soil particles to be detached (detachability) and to be transported (transportability). These properties are affected by soil texture and influence the sediment load G to be transported by flow. The actual sediment load depends on the transport capacity Tc of the flow, which is the maximum amount of sediment, with given sizes and specific weight, that can be transported by a flow of known hydraulic characteristics.According to Jiang et al. (2018) the hydraulic mechanisms of soil erosion for steep slopes are different from those for gentle slopes. Recent research on Tc equations exploring slopes steeper than 18% (Ali et al., 2013; Zhang et al., 2009; Wu et al., 2016) established that Tc relationships designed for gentle slopes (<18%) are unsuitable to be applied to steep slopes (17&#8211;47%). Also Peng et al. (2015) noticed that <<there has been little research concerning rill flow on steep slopes (e.g. slope gradients higher than 10&#176;)>>. In other words, the slope of 18% could be used to distinguish between the &#8220;gentle slope&#8221; and the &#8220;steep slope&#8221; case for the recognized difference in hydraulic and sediment transport variables.The applicability of a theoretical rill flow resistance equation, based on the integration of a power velocity distribution (Barenblatt, 1979; 1987), was tested using measurements carried out in mobile rills shaped on plots having different slopes (9, 14, 15, 18, 22, 24, 25 and 26%) and soil textures (clay fractions ranging from 32.7% to 73% and silt of 19.9% &#8211; 30.9%), and measurements available in literature (Jiang et al. (2018), Huang et al. (2020) and Yang et al. (2020)).The Darcy-Weisbach friction factor resulted dependent on slope, Froude number, Reynolds number and CLAY and SILT percentages, which represent soil transportability and detachability, respectively. This theoretical approach was applied to two different databases distinguished by the slope threshold of 18%. The results showed that, for gentle slopes (< 18%), the Darcy-Weisbach friction factor increases with slope, CLAY and SILT content. Taking into account that for gentle slopes the hydraulic characteristics limit the transport capacity, for this condition Tc and the sediment load G are both limiting factors.For steep slopes (> 18%), the flow resistance increases with slope and the ratio between SILT and CLAY percentage. Steep slopes determine high values of the transport capacity, which is consequently not a limiting factor. Thus, in this condition the actual sediment load is determined exclusively by the ratio between SILT and CLAY percentage. In other words, the only limiting factor for a steep slope condition is the sediment which can be transported (i.e. the sediment load G), affected by its soil detachability and transportability.

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Turbulence Intensity Scaling: A Fugue

Fluids ◽

10.3390/fluids4040180 ◽

2019 ◽

Vol 4 (4) ◽

pp. 180 ◽

Cited By ~ 3

Author(s):

Nils T. Basse

Keyword(s):

Reynolds Number ◽

Friction Factor ◽

Turbulence Intensity ◽

Pipe Flow ◽

Rough Wall ◽

Flow Measurements ◽

Flow Turbulence ◽

Intensity Scaling ◽

Grain Roughness ◽

Made In

We study streamwise turbulence intensity definitions using smooth- and rough-wall pipe flow measurements made in the Princeton Superpipe. Scaling of turbulence intensity with the bulk (and friction) Reynolds number is provided for the definitions. The turbulence intensity scales with the friction factor for both smooth- and rough-wall pipe flow. Turbulence intensity definitions providing the best description of the measurements are identified. A procedure to calculate the turbulence intensity based on the bulk Reynolds number (and the sand-grain roughness for rough-wall pipe flow) is outlined.

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Experimental Investigation on the Flow Resistance of a Staged Fuel Injector with Thermal Protection

International Journal of Aerospace Engineering ◽

10.1155/2021/8881460 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Jingyu Zhang ◽

Xinyi Wang ◽

Yu Wu ◽

Xiaomin He

Keyword(s):

Experimental Investigation ◽

Reynolds Number ◽

Friction Factor ◽

Flow Resistance ◽

High Efficiency ◽

Thermal Protection ◽

Multiple Point ◽

Inlet Temperature ◽

Fuel Injector ◽

Effective Measure

The multistaged rotating swirling usually adopts the staged combustion and multiple point fuel supply, which has the advantages of high efficiency and low emissions. However, the high inlet temperature rise will cause autooxidation and fuel coking. Multiple fuel circuit mutual cooling technology by using different flight conditions is an effective measure for the thermal protection of the nozzle. But the complicated fuel circuit configuration inevitably increase the flow resistance in the fuel jet. This paper presents an experimental investigation of flow resistance of a triple-stage rotating swirling nozzle, concerning the effects of various factors on total pressure loss and friction factor in nozzle fuel circuit. The factors include fuel velocity V f , i , inlet temperature T f , i , and inlet Reynolds number Re f , i . The results show that the complicated fuel-cooled structure made flow resistance of the pilot fuel circuit much bigger than the main one. Meanwhile, the empirical correlations between the friction factor and the inlet Reynolds number have been fitted, which can be the reference for engineering design.

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Evaluating the Effects of Sediment Transport on Pipe Flow Resistance

Water ◽

10.3390/w13152091 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2091

Author(s):

Vito Ferro ◽

Alessio Nicosia

Keyword(s):

Velocity Profile ◽

Pipe Flow ◽

Power Distribution ◽

Flow Resistance ◽

Unit Length ◽

Particle Diameter ◽

Self Similarity ◽

Sediment Size ◽

The Mean ◽

The Relationship

In this paper, the applicability of a theoretical flow resistance law to sediment-laden flow in pipes is tested. At first, the incomplete self-similarity (ISS) theory is applied to deduce the velocity profile and the corresponding flow resistance law. Then the available database of measurements carried out by clear water and sediment-laden flows with sediments having a quasi-uniform sediment size and three different values of the mean particle diameter Dm (0.88 mm, 0.41 mm and 0.30 mm) are used to calibrate the parameter of the power-velocity profile). The fitting of the measured local velocity to the power distribution demonstrates that (i) for clear flow the exponent δ) can be estimated by the equation of Castaing et al. and (ii) for the sediment-laden flows δ is related to the diameter Dm. A relationship for estimating the parameter Гv obtained by the power-velocity profile) and that Гf of the flow resistance law) is theoretically deduced. The relationship between the parameter Гv, the head loss per unit length and the pipe flow Froude number is also obtained by the available sediment-laden pipe flow data. Finally, the procedure to estimate the Darcy–Weisbach friction factor is tested by the available measurements.

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Numerical and Experimental Analysis of Turbulent Flow in Corrugated Pipes

Journal of Fluids Engineering ◽

10.1115/1.4002035 ◽

2010 ◽

Vol 132 (7) ◽

Cited By ~ 18

Author(s):

Henrique Stel ◽

Rigoberto E. M. Morales ◽

Admilson T. Franco ◽

Silvio L. M. Junqueira ◽

Raul H. Erthal ◽

...

Keyword(s):

Reynolds Number ◽

Pressure Drop ◽

Turbulent Flow ◽

Friction Factor ◽

Turbulence Models ◽

Reynolds Numbers ◽

Velocity Magnitude ◽

Geometric Configurations ◽

Corrugated Surfaces ◽

Friction Factors

This article describes a numerical and experimental investigation of turbulent flow in pipes with periodic “d-type” corrugations. Four geometric configurations of d-type corrugated surfaces with different groove heights and lengths are evaluated, and calculations for Reynolds numbers ranging from 5000 to 100,000 are performed. The numerical analysis is carried out using computational fluid dynamics, and two turbulence models are considered: the two-equation, low-Reynolds-number Chen–Kim k-ε turbulence model, for which several flow properties such as friction factor, Reynolds stress, and turbulence kinetic energy are computed, and the algebraic LVEL model, used only to compute the friction factors and a velocity magnitude profile for comparison. An experimental loop is designed to perform pressure-drop measurements of turbulent water flow in corrugated pipes for the different geometric configurations. Pressure-drop values are correlated with the friction factor to validate the numerical results. These show that, in general, the magnitudes of all the flow quantities analyzed increase near the corrugated wall and that this increase tends to be more significant for higher Reynolds numbers as well as for larger grooves. According to previous studies, these results may be related to enhanced momentum transfer between the groove and core flow as the Reynolds number and groove length increase. Numerical friction factors for both the Chen–Kim k-ε and LVEL turbulence models show good agreement with the experimental measurements.

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Overland Flow Resistance Law under Sparse Stem Vegetation Coverage

Water ◽

10.3390/w13121657 ◽

2021 ◽

Vol 13 (12) ◽

pp. 1657

Author(s):

Jingzhou Zhang ◽

Shengtang Zhang ◽

Si Chen ◽

Ming Liu ◽

Xuefeng Xu ◽

...

Keyword(s):

Flow Resistance ◽

Overland Flow ◽

Vegetation Coverage ◽

Dominant Factor ◽

Roughness Coefficient ◽

Hydraulic Parameters ◽

Slope Condition ◽

Manning Roughness ◽

The Relationship ◽

Manning Roughness Coefficient

To explore the characteristics of overland flow resistance under the condition of sparse vegetative stem coverage and improve the basic theoretical research of overland flow, the resistance characteristics of overland flow were systematically investigated under four slope gradients (S), seven flow discharges (Q), and six degrees of vegetation coverage (Cr). The results show that the Manning roughness coefficient (n) changes with the ratio of water depth to vegetation height (h/hv) while the Reynolds number (Re), Froude number (Fr), and slope (S) are closely related to vegetation coverage. Meanwhile, h/hv, Re, and Cr have strong positive correlations with n, while Fr and S have strong negative correlations with n. Through data regression analysis, a power function relationship between n and hydraulic parameters was observed and sensitivity analysis was performed. It was concluded that the relationship between n and h/hv, Re, Cr, Q, and S shows the same law; in particular, for sparse stem vegetation coverage, Cr is the dominant factor affecting overland flow resistance under zero slope condition, while Cr is no longer the first dominant factor affecting overland flow resistance under non-zero slope condition. In the relationship between n and Fr, Cr has the least effect on overland flow resistance. This indicates that when Manning roughness coefficient is correlated with different hydraulic parameters, the same vegetation coverage has different effects on overland flow resistance. Therefore, it is necessary to study overland flow resistance under the condition of sparse stalk vegetation coverage.

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A Combined Packed-Bed Friction Factor Equation: Extension to Higher Reynolds Number with Wall Effects

AIChE Journal ◽

10.1002/aic.14034 ◽

2013 ◽

Vol 59 (3) ◽

pp. 703-706 ◽

Cited By ~ 20

Author(s):

Luke D. Harrison ◽

Kyle M. Brunner ◽

William C. Hecker

Keyword(s):

Reynolds Number ◽

Friction Factor ◽

Packed Bed ◽

Wall Effects ◽

Bed Friction ◽

Factor Equation

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Thermal Performance Assessment of Turbulent Flow Through Dimpled Tubes

2010 14th International Heat Transfer Conference, Volume 2 ◽

10.1115/ihtc14-22503 ◽

2010 ◽

Cited By ~ 2

Author(s):

Pornchai Nivesrangsan ◽

Somsak Pethkool ◽

Kwanchai Nanan ◽

Monsak Pimsarn ◽

Smith Eiamsa-ard

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Friction Factor ◽

Heat Transfer Rate ◽

Thermal Performance ◽

Transfer Rate ◽

Staggered Arrangement ◽

Plain Tube ◽

Pitch Ratio ◽

Surface Patterns

This paper presents the heat transfer augmentation and friction factor characteristics by means of dimpled tubes. The experiments were conducted using the dimpled tubes with two different dimpled-surface patterns including aligned arrangement (A-A) and staggered arrangement (S-A), each with two pitch ratios (PR = p/Di = 0.6 and 1.0), for Reynolds number ranging from 9800 to 67,000. The experimental results achieved from the dimpled tubes are compared with those obtained from the plain tube. Evidently, the dimpled tubes with both arrangements offer higher heat transfer rates compared to the plain tube and the dimpled tube with staggered arrangement shows an advantage on the basis of heat transfer enhancement over the dimpled tube with aligned arrangement. The increase in heat transfer rate with reducing pitch ratio is due to the higher turbulent intensity imparted to the flow between the dimple surfaces. The mean heat transfer rate offered by the dimpled tube with staggered arrangement (S-A) at the lowest pitch ratio (PR = 0.6), is higher than those provided by the plain tube and the dimpled tube with aligned arrangement (A-A) at the same PR by around 127% and 8%, respectively. The empirical correlations developed in terms of pitch ratio (PR), Prandtl number (Pr) and Reynolds number, are fitted the experimental data within ±8% and ±2% for Nusselt number (Nu) and friction factor (f), respectively. In addition, the thermal performance factors under an equal pumping power constraint of the dimple tubes for both dimpled-surface arrangements are also determined.

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