scholarly journals Directional Passive Condensate Film Drainage on a Horizontal Surface With Periodic Asymmetrical Structures

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Shashank Natesh ◽  
Eric Truong ◽  
Vinod Narayanan ◽  
Sushil Bhavnani
Keyword(s):  
Mass Flux ◽  
Bond Number ◽  
Horizontal Surface ◽  
Control Surface ◽  
Test Surface ◽  
Spanwise Direction ◽  
Flux Rate ◽  
Condensate Film ◽  
Film Drainage ◽  
Visualization Experiments

Condensation of a highly wetting fluid on a horizontal surface with asymmetric millimeter-sized ratchets and periodically located film drainage pathways (DPs) in the spanwise direction is characterized. The hypothesis to be tested is whether the geometry would result in a net steady-state preferential drainage of the condensate film. Experiments are performed using PF5060 on a brass surface with ratchets of 3 mm pitch and 75–15 deg asymmetry. Drainage pathways are varied in density as nondimensional drainage pathways per meter depth ranging from 133 to 400. Experiments are performed at varied wall subcooling temperatures from 1 to 10 °C. Results of the asymmetric ratchet are compared against a control test surface with 45–45 deg symmetric ratchets. Both global and film visualization experiments are performed to characterize the differences in condensation between the symmetric and asymmetric surfaces. Global mass collection results indicate that all characterized asymmetric ratchet surfaces exhibit a net directional drainage of condensate while the symmetric control surface exhibited no preferential drainage. Among the asymmetric ratchets, the total mass flux rate increase with decrease in drainage pathway density, while the net mass flux rate increased with pathway density. Visualization of the condensate film was performed to explain the trends in net drainage with subcooling for different drainage pathway densities. For small drainage path density surfaces, a two-dimensional analytical model was developed to further characterize the effect of ratchet angle and Bond number on the net preferential drainage.

scholarly journals Film Cooling From Spanwise Oriented Holes in Two Staggered Rows

1995 ◽  
Author(s):  
Phillip M. Ligrani ◽  
Anthony E. Ramsey
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Flux Ratio ◽  
Test Surface ◽  
Spanwise Direction ◽  
Transfer Coefficients ◽  
Blowing Ratio ◽  
Streamwise Location ◽  
Adiabatic Effectiveness ◽  
Lift Off

Adiabatic effectiveness and iso-energetic heat transfer coefficients are presented from measurements downstream of film-cooling holes inclined at 30 degrees with respect to the test surface in spanwise/normal planes. With this configuration, holes are spaced 3d apart in the spanwise direction and 4d in the streamwise direction in two staggered rows. Results are presented for an injectant to freestream density ratio near 1.0, and injection blowing ratios from 0.5 to 1.5. Spanwise-averaged adiabatic effectiveness values downstream of the spanwise/normal plane holes are significantly higher than values measured downstream of simple angle holes for x/d<25–70 (depending on blowing ratio) when compared for the same normalized streamwise location, blowing ratio, and spanwise and streamwise hole spacings. Differences are principally due to different coalescence of injectant accumulations from the two different rows of holes, as well as significantly different lift-off dependence on momentum flux ratio. Spanwise-averaged iso-energetic Stanton number ratios are somewhat higher than ones measured downstream of other simple and compound angle configurations studied. Values range between 1.0 and 1.41, increase with blowing ratio at each streamwise station, and show little variation with streamwise location for each value of blowing ratio tested.

scholarly journals EROSIVE POTENTIAL OF SPORTS BEVERAGES ON HUMAN ENAMEL “IN VITRO”

2018 ◽  
Vol 24 (5) ◽  
pp. 386-390
Author(s):  
Dalila Meazza Damo ◽  
Guilherme Anziliero Arossi ◽  
Helena Alvez da Silva ◽  
Leonardo Haerter dos Santos ◽  
Diego Rafael Kappaun
Keyword(s):  
Vickers Microhardness ◽  
Tooth Enamel ◽  
Low Ph ◽  
Control Surface ◽  
Test Surface ◽  
Results Of Treatment ◽  
Sports Drinks ◽  
Human Enamel ◽  
The Mean

ABSTRACT Introduction: The low pH of sports drinks may cause tooth enamel demineralization. Objective: To measure Vickers hardness of human enamel exposed to sports drinks. Methods: Human molars were used to collect the enamel samples. Each sample had a test surface (exposed to the drinks) and a control surface (unexposed). The samples were exposed to isotonic drinks Gatorade and Powerade, and to maltodextrin drinks Malto Advanced and Malto Active, for 10 minutes every 12 hours over 30 days. The Vickers microhardness test was conducted with three indentations on each surface. The mean of the indentations within each group was considered in the statistical analysis. Sports drinks variables were analyzed with ANOVA/Tukey (p≤0.01). The independent t-test was used in the comparison between the control and test surfaces of each drink (p ≤ 0.05). Results: Enamel exposure to Gatorade (p = 0.000) Malto Advanced (p = 0.000) and Malto Active (p = 0.000) was seen to significantly reduce microhardness, while the isotonic drink Powerade had no significant effect on enamel (p = 0.248). Conclusion: It was concluded that with the exception of the isotonic drink Powerade, all the sports drinks tested caused a reduction in the microhardness of human enamel. Evidence Level III; Therapeutic studies - Investigating the Results of Treatment.

Experimental study on the effect of air throttling on supersonic combustion

2016 ◽  
Vol 232 (3) ◽  
pp. 472-480 ◽  
Author(s):  
Ye Tian ◽  
Shunhua Yang ◽  
Baoguo Xiao ◽  
Jialing Le
Keyword(s):  
Experimental Study ◽  
Mass Flux ◽  
Equivalence Ratio ◽  
Flame Stabilization ◽  
Wall Pressure ◽  
Supersonic Combustion ◽  
Reacting Flow ◽  
Flux Rate ◽  
Shock Train ◽  
Scramjet Combustor

The effect of air throttling on supersonic combustion was investigated by experiments in the present paper. Our results indicated that, in the non-reacting flow, a shock train could be generated in the scramjet combustor due to the increased backpressure caused by air throttling, and the wall pressure increased obviously. But when the mass flux rate of air throttling was not large enough, the shock train would oscillate with the flow. In the reacting flow, the flame stabilization was achieved in the combustor without air throttling when the equivalence ratio of kerosene was 0.2 and 0.31, but the flame was blown off when the equivalence ratio of kerosene was 0.45. On the contrary, the kerosene (equivalence ratio: 0.45) was ignited successfully in the combustor with air throttling, and it kept burning all the time in the cases with air throttling −5% (the flux of air throttling was 5% of the inflow flux) and with air throttling −14% (the flux of air throttling was 14% of the inflow flux), but the flame was blown off in the case with air throttling −1.1% after kerosene had burnt 70 ms. The flux of air throttling should be large enough to achieve flame stabilization, and the hydrogen and air throttling should both exist all the time in order to keep the flame burning steadily.

Rivulet Instability with Effect of Coriolis Force

2006 ◽  
Vol 22 (3) ◽  
pp. 221-227 ◽  
Author(s):  
H.-C. Cho ◽  
F.-C. Chou
Keyword(s):  
Coriolis Force ◽  
Critical Radius ◽  
Deflection Angle ◽  
Characteristic Length ◽  
Bond Number ◽  
Viscous Force ◽  
Fingering Instability ◽  
High Bond ◽  
The Deflection Angle ◽  
Visualization Experiments

AbstractThe effect of Coriolis force on the rivulet (fingering) instability, the onset of rivulet phenomena during spin coating, is investigated by flow visualization experiments incorporating with dimensional analysis. This study demonstrates that the Coriolis force will affect significantly the critical radius of rivulet instability and the deflection angle of instability rivulet. For the cases of low Bond number, the effect of Coriolis force is a stabilizing factor, and the dimensionless critical radius increases slightly with increasing rotational Reynolds number Reω. In the case of high Bond number, the effect of Coriolis force becomes a destabilizing factor while Reω < 1, and a characteristic length is found by balancing the viscous force with the surface tension. For Reω > 1, the radial Corilois force, which is always pointing inward, plays a stabilizing role with magnitude Reω2.

scholarly journals A global climatology of stratosphere–troposphere exchange using the ERA-Interim data set from 1979 to 2011

2014 ◽  
Vol 14 (2) ◽  
pp. 913-937 ◽  
Author(s):  
B. Škerlak ◽  
M. Sprenger ◽  
H. Wernli
Keyword(s):  
North America ◽  
Tibetan Plateau ◽  
Mass Flux ◽  
West Coast ◽  
Surface Ozone ◽  
Control Surface ◽  
The Tibetan Plateau ◽  
The West ◽  
Data Set ◽  
Ozone Flux

Abstract. In this study we use the ERA-Interim reanalysis data set from the European Centre for Medium-Range Weather Forecasts (ECMWF) and a refined version of a previously developed Lagrangian methodology to compile a global 33 yr climatology of stratosphere–troposphere exchange (STE) from 1979 to 2011. Fluxes of mass and ozone are calculated across the tropopause, pressure surfaces in the troposphere, and the top of the planetary boundary layer (PBL). This climatology provides a state-of-the-art quantification of the geographical distribution of STE and the preferred transport pathways, as well as insight into the temporal evolution of STE during the last 33 yr. We confirm the distinct zonal and seasonal asymmetry found in previous studies using comparable methods. The subset of "deep STE", where stratospheric air reaches the PBL within 4 days or vice versa, shows especially strong geographical and seasonal variations. The global hotspots for deep STE are found along the west coast of North America and over the Tibetan Plateau, especially in boreal winter and spring. An analysis of the time series reveals significant positive trends of the net downward mass flux and of deep STE in both directions, which are particularly large over North America. The downward ozone flux across the tropopause is dominated by the seasonal cycle of ozone concentrations at the tropopause and peaks in summer, when the mass flux is nearly at its minimum. For the subset of deep STE events, the situation is reversed and the downward ozone flux into the PBL is dominated by the mass flux and peaks in early spring. Thus surface ozone concentration along the west coast of North America and around the Tibetan Plateau are likely to be influenced by deep stratospheric intrusions. We discuss the sensitivity of our results on the choice of the control surface representing the tropopause, the horizontal and vertical resolution of the trajectory starting grid, and the minimum residence time τ used to filter out transient STE trajectories.

scholarly journals Strategies for Estimation of Gas Mass Flux Rate Between Surface and the Atmosphere

10.5772/35201 ◽  
2012 ◽  
Author(s):  
Haroldo F. de Campos Velho ◽  
Dbora R. ◽  
Eduardo F.P. da Luz ◽  
Fabiana F.
Keyword(s):  
Mass Flux ◽  
Flux Rate

Film Size During Bubble Collision With a Solid Surface

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Travis S. Emery ◽  
Satish G. Kandlikar
Keyword(s):  
Solid Surface ◽  
Froth Flotation ◽  
Bond Number ◽  
Film Drainage ◽  
Drainage Rate ◽  
Archimedes Number ◽  
Experimental Parameters ◽  
Bubble Collision ◽  
The Impact ◽  
The Relationship

The impact and bounce of a bubble with a solid surface is of significant interest to many industrial processes such as froth flotation and biomedical engineering. During the impact, a liquid film becomes trapped between the bubble and the solid surface. The pressure buildup in this film leads to the generation of a film force. The drainage rate of this film plays a crucial role in dictating the bouncing process and is known to be a function of the radial film size. However, radial film size is not an easily attained experimental measurement and requires advanced instrumentation to capture. The bouncing process has been characterized using nondimensional numbers that are representative of the bubble collision and film drainage phenomena. These are: Bond number (Bo), Archimedes number (Ar), Froude number (Fr), and the ratio of film force to buoyancy force (FF/FB). These numbers are used to define a predictive function for film radius. Experimentally validated numerical modeling has been implemented to determine the relationship between the four nondimensional numbers, and a quasi-static model is employed to relate the film force to the radial film size. Comparison of our experimental results is in agreement with the predicted film size within ±20%. From these results, the radial film size during bubble impact with a solid surface may be predicted using the easily measurable experimental parameters of bubble size, bubble impact velocity, and the liquid properties.

Film Cooling From a Single Row of Holes Oriented in Spanwise/Normal Planes

1997 ◽  
Vol 119 (4) ◽  
pp. 770-776 ◽  
Author(s):  
P. M. Ligrani ◽  
A. E. Ramsey
Keyword(s):  
Film Cooling ◽  
Test Surface ◽  
Spanwise Direction ◽  
Single Row ◽  
Local Maxima ◽  
Blowing Ratio ◽  
Streamwise Location ◽  
Structure Of Flow ◽  
Adiabatic Effectiveness ◽  
Lift Off

Experimental results are presented that describe the development and structure of flow downstream of a single row of film-cooling holes inclined at 30 deg from the test surface in spanwise/normal planes. With this configuration, holes are spaced 6d apart in the spanwise direction in a single row. Results are presented for a ratio of injectant density to free-stream density near 1.0, and injection blowing ratios from 0.5 to 1.5. Compared to results measured downstream of simple angle (streamwise) oriented holes, spanwise-averaged adiabatic effectiveness values are significantly higher for the same spanwise hole spacing, normalized streamwise location x/d, and blowing ratio m when m = 1.0 and 1.5 for x/d < 80. The injectant from the spanwise/normal holes is also less likely to lift off of the test surface than injectant from simple angle holes. This is because lateral components of momentum keep higher concentrations of injectant in closer proximity to the surface. As a result, local adiabatic effectiveness values show significantly greater spanwise variations and higher local maxima at locations immediately downstream of the holes. Spanwise-averaged iso-energetic Stanton number ratios range between 1.07 and 1.26, which are significantly higher than values measured downstream of two other injection configurations (one of which is simple angle, streamwise holes) when compared at the same x/d and blowing ratio.

Film Cooling and Thermal Field Measurements for Staggered Rows of Rectangular-Shaped Film Cooling Holes

2003 ◽  
Author(s):  
Dong Ho Rhee ◽  
Youn Seok Lee ◽  
Young Bong Kim ◽  
Hyung Hee Cho
Keyword(s):  
Film Cooling ◽  
Lateral Spreading ◽  
Temperature Fields ◽  
Test Surface ◽  
Spanwise Direction ◽  
Rectangular Hole ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Film Cooling Holes

An experimental study has been conducted to measure the temperature fields and the local film cooling effectiveness for two and three staggered rows of the rectangular-shaped film cooling holes with various blowing rates. Three different cooling hole shapes such as a straight rectangular hole, a rectangular hole with laterally expanded exit and a circular hole are tested. The rectangular cross-section has the aspect ratio of 2 at the hole inlet with the hydraulic diameter of 10 mm. The area ratio of the exit to the hole inlet is 1.8 for the rectangular hole with expanded exit, which is similar to a two-dimensional slot. The holes are spaced 3d apart in the spanwise direction and 4d apart in the streamwise direction with a staggered arrangement. Temperature fields are acquired using a three-axis traversing system equipped with a thermocouple rake. A thermochromic liquid crystals technique is applied to determine adiabatic film cooling effectiveness values and heat transfer coefficients on the test surface. The results show that the rectangular-shaped holes provide better performance than the cylindrical holes because the penetration of coolant is reduced and the lateral spreading of coolant is promoted. For rows of film cooling holes, the film cooling performance decreases with increasing blowing rate. However, the difference of hole shapes and blowing rates for film cooling performance is reduced with increasing the row of cooling holes.

Film-Cooling From Holes With Compound Angle Orientations: Part 1—Results Downstream of Two Staggered Rows of Holes With 3d Spanwise Spacing

1994 ◽  
Vol 116 (2) ◽  
pp. 341-352 ◽  
Author(s):  
P. M. Ligrani ◽  
J. M. Wigle ◽  
S. Ciriello ◽  
S. M. Jackson
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Test Surface ◽  
Spanwise Direction ◽  
Normal Plane ◽  
Streamwise Location ◽  
Structure Of Flow ◽  
Film Cooling Holes ◽  
Compound Angle ◽  
Angle Orientation

Experimental results are presented that describe the development and structure of flow downstream of two staggered rows of film-cooling holes with compound angle orientations. With this configuration, holes are spaced 3d apart in the spanwise direction, inclined at 35 deg with respect to the test surface when projected into the streamwise/normal plane, and inclined at 30 deg with respect to the test surface when projected into the spanwise/normal plane. Results are presented for an injectant to free-stream density ratio near 1.0, and injection blowing ratios from 0.5 to 1.50. Comparisons are made with measurements from two other configurations to determine: (1) the effects of hole angle orientation for constant spanwise hole spacing, and (2) the effects of spanwise hole spacing when the hole angle orientation is maintained constant. Results from the first comparison show that the compound angle injection configuration provides significantly improved film-cooling protection compared to a simple angle configuration for the same spanwise hole spacing, normalized streamwise location x/d, and blowing ratio m, for x/d<60. At x/d>60, spanwise-averaged adiabatic effectiveness data downstream of the two configurations generally cover about the same range. Results from the second comparison show that spanwise-averaged effectiveness values are 25 to 40 percent higher when 3d spanwise hole spacing is employed compared to 3.9d spanwise hole spacing for the same m and x/d, for x/d<40. At x/d>40, differences between the two configurations range from 12 to 30 percent. Results from all configurations studied show that spanwise-averaged iso-energetic Stanton number ratios cover approximately the same range of values and show roughly the same trends, ranging between 1.0 and 1.25. In particular, Stf/St0 values increase with m at each x/d, and show little variation with x/d for each value of m tested.

Sign in / Sign up

Export Citation Format

Share Document