Wavy Rib Research Articles

Research on improving heat transfer performance by using wavy ribs with different cross sections

Based on the change of the cross section in blade internal cooling channel rib caused by the service wear, starting from the widely used rectangular cross section, the most likely isosceles trapezoid and rectangular-semicircular cross section are considered, and the extreme design of the cross section (isosceles triangle) and the tentative exploration (spindle) are carried out. In this paper, the numerical calculation of SST k-ω turbulence model and the experimental research method of TSP measurement are used to thoroughly investigate the impact mechanisms of five different wavy rib cross-sections on the flow and heat transfer in turbine blade ribbed channels. The results show that different rib cross-sections alter the flow and heat transfer in channel by modifying flow allocation in height and width directions. The inclined sidewalls of the wavy ribs accumulate most of cooling air near the rib, which is the ultimate cause of the significant cooling effect. Under small rib radius and small rib angle, the heat transfer advantages of isosceles triangle and isosceles trapezoid cross-section wavy ribs are more obvious, which are increased by 14.88 % and 20.66 % respectively, but their friction factor is also 1.2 ∼ 2.0 times that of rectangular cross-section. The heat transfer of the large rib height on the isosceles triangular and isosceles trapezoidal cross-section wavy ribs is increased by 73.29 % and 185.31 %. Changes in Reynolds number have minimal impact on the friction factor, but significantly impact the overall heat transfer.

Analyzing the impact of sinusoidal wavy rib geometric parameters on turbine blade thermal and fluid dynamics

The wavy rib is a spoiler structure designed to improve flow and heat transfer within turbine blade cooling channels, offering valuable insights for efficient cooling design in aerospace applications. This study employs a blend of experimental validation and detailed numerical simulations to investigate how rib height, amplitude, and discontinuity size collectively impact heat transfer enhancement and flow resistance in wavy ribs. By integrating TSP temperature field measurements with SST k-ω numerical calculations across 8 rib heights, 7 amplitudes, and 9 discontinuities at Reynolds numbers ranging from 10000 to 40000, the research reveals intricate relationships between these parameters. Studies have shown that there is a strong interaction between amplitude and rib height, as well as amplitude and discontinuity. Under small amplitude, Nu/Nu0 increases monotonously with the increase of rib height, but increases first and then decreases under large amplitude. When the discontinuity is small, the dimensionless Nusselt number (Nu/Nu0) of the ribbed wall increases first and then decreases with the increase of rib height, while it increases monotonously when the discontinuity is large. In contrast, the interaction between amplitude and discontinuity is weak. The ribbed wall with the greatest heat transfer improvement has Nu/Nu0 nearly 80 % higher than the reference wavy rib scheme, but it also has the highest corresponding pressure loss. The best overall thermal performance is 20 % higher than the reference structure, and the ribbed wall Nu/Nu0 is also increased by 24 %. The change of Reynolds number at the inlet of the channel has little effect on the wall Nu/Nu0 and pressure loss of the wavy rib channel.

Effects of non-uniform wavy ribs on flow and heat transfer characteristics of turbine blade cooling channel

Aiming at the problem of reduced heat transfer performance and uneven distribution along the ribbed channel in aero-engine turbine blades, the influence mechanism of rib height, rib angle and fillet radius on the flow and heat transfer characteristics of wavy rib cooling channel under different inlet Reynolds numbers is analyzed by experimental and numerical methods. The research illustrates that the non-uniform change of the rib height has the most profound influence on the heat transfer performance of the ribbed channel. Schemes featuring larger initial and final rib heights demonstrate superior heat transfer performance and uniformity, with the friction factor primarily determined by the maximum rib height. The optimal rib height variation scheme shows a 22.6 % increase in overall Nu/Nu0, with only a 6 % reduction in heat transfer evenness. The non-uniform variation of rib angle and fillet radius mainly affects the local heat transfer and friction factor. Increasing Reynolds number, the distribution of friction factor of the large rib height scheme changes more drastically. At a large Reynolds number (Re = 40000), the enhanced heat transfer in the middle and rear sections of the channel due to the larger rib angle and fillet radius comes at the cost of increased pressure loss.

Effects of wavy ribs on vortex generation and thermal-hydraulic performance in a rotating rectangular channel

An experimental and numerical study has been conducted to analyze the effects of rib configurations on heat transfer in U-turn rotating rectangular channels with smooth walls. A new model of a wavy rib is studied and compared with traditional ribs in a rectangular cross-section. Heat transfer coefficients for all rib configurations were measured from Reynolds numbers 4000 to 12000, whereas rotation numbers ranged from 0.025 to 0.15. Computational fluid dynamics (CFD) with the k-ω SST turbulence model were utilized to investigate turbulent kinetic energies, Nusselt numbers, flow structure, and thermal performance. The results indicated that the thermal performance factor of wavy ribs was 22.1%–28.7% higher than the rectangular cross-section ribs. The effects of Coriolis and rotational buoyancy result in growth and reduction of heat transfer in the leading and trailing walls. The simulation results are supported by experimental data with a difference of 3 to 10% for all samples, respectively.

Heat transfer and flow characteristics of U-shaped cooling channels with novel wavy ribs under stationary and rotating conditions

Wavy rib is a kind of novel turbulator that can effectively improve the ribbed wall heat transfer of cooling channel and produce acceptable friction loss. Meanwhile, it has the advantage of simple structure. In this paper, the effects of wavy ribs on the heat transfer distributions of ribbed walls, side walls, and top wall are numerically studied in stationary and rotating U-shaped channels. The flow characteristics of cooling air are also analyzed. Taking the 45° V-shaped ribs as the reference scheme, the high-performance wavy ribs that have better heat transfer performance on ribbed wall and induce the same friction loss are selected. The channel aspect ratio is 1, with the height of 12.7 mm. The investigated Reynolds number is 25,000, and the rotation number is 0, 0.2, 0.3 and 0.4. Rib height (e-3e), rib round radius (0–5 mm), and rib angle (20–55°) are the three major geometrical parameters of wavy rib. The results show that, the diversion effect of wavy ribs on cooling air is the reason of friction loss suppression. On the one hand, the wavy ribs confine the fluid disturbance on side walls, leading to the heat transfer reduction. On the other hand, the impingement of cooling air on the channel top wall is strengthened, which improves the wall heat transfer. In stationary and rotating conditions, the high-performance wavy ribs increase the heat flux on heated surface corresponding to the ribbed wall by 5–21% and 4–24% respectively, and weaken the effect of Coriolis force on the heat transfer of the first pass. With the increase of rotation number, the friction penalty and heat transfer of leading side ribbed wall decrease, while the heat transfer of trailing side ribbed wall slightly increases, showing that those high-performance wavy ribs have a good versatility at multiple rotation numbers.

Numerical predictions on heat transfer and flow characteristics in a straight channel with different geometric parameters wavy ribs

A wavy rib is presented and its influences on the performance of a non-rotating straight channel are studied numerically. For each geometric parameter of wavy rib, the target surfaces are determined and the corresponding performance parameters are evaluated, to explore how wavy ribs affect channel heat transfer, especially the ribbed wall. Rib height (he = e − 3e), rib round radius (r = 0–5 mm), and rib angle (α = 20–55°) are the three key geometric parameters to study. The investigated Reynolds number is 25,000 and the channel aspect ratio is 1:1. The results indicate that three geometric parameters affect the channel performance by altering the diversion and obstruction of wavy ribs on cooling air. Among them, rib height is a dominant geometric parameter that determines the heat transfer improvement, while rib round radius and rib angle are mainly employed to reduce the friction loss. High rib height and large rib round radius, which can significantly increase heat transfer area and effectively decrease friction loss, respectively, are the basic features of high-performance wavy ribs. Meanwhile, the wavy ribs after optimal design perform better than 45° V-shaped ribs in heat transfer enhancement at the same friction penalty.

Thermal-hydraulic performance of longitudinal wavy rib along wavy two-pass channel

An experimental study investigates the thermal-hydraulic characteristics of the novel longitudinal wavy ribs along a wavy two-pass square channel. The detailed Nusselt number (Nu) distributions over the ribbed wavy endwall are measured using the steady-state infrared thermography method together with the Fanning friction factors (f) evaluated from the pressure drop measurements. Relative heat transfer enhancements (HTE) and pressure drop augmentations for present HTE element are disclosed by comparing the Nu and f data measured from the wavy channels with and without wavy ribs, as well as the straight two-pass channels with V- or W-ribs. Acting by the additional HTE mechanisms induced by the wavy ribs, the regionally averaged Nu over inlet leg, sharp bend and outlet leg of present ribbed two-pass wavy channel are respectively raised to 5.8–5.5, 6.04–5.52, 5.81–4.94 and 5.7–5.12 times of Dittus-Boelter levels at 5000 < Re < 30,000. Accompanying with the channel averaged f factors in the range of 43.67–21.43 times of Balssius correlation values, the thermal performance factors (TPF) of 1.51–1.62 are achieved for present ribbed two-pass wavy channel. To assist relevant engineering applications, two set of empirical correlations permitting the evaluations of regionally averaged Nu and the channel averaged f are devised.

Effects of continuous wavy ribs on heat transfer and cooling air flow in a square single-pass channel of turbine blade

A wavy rib with the simple structure is proposed for the internal cooling channel in turbine blade, in order to enhance heat transfer and reduce pressure loss. The heat transfer performance and flow characteristics of a single-pass, stationary channel with wavy ribs are studied by numerical method. The channel width is 12.7 mm, with an aspect ratio of 1. Four major geometric parameters of wavy rib, including rib height (he = e−3e), rib round radius (r = 0–5 mm), rib angle (α = 20–55°) and rib thickness (th = 0.5e−2e) are investigated in optimal design. Furthermore, the potential high-performance wavy ribs are explored as well. The investigated Reynolds number is 10,000–40,000. Meanwhile, the typical 45° V-shaped ribs which have high heat transfer improvement are selected as the reference scheme of wavy rib. Both the rib height (e) and rib width are 1.58 mm, and the rib pitch P/e is 10. From the results, flow behavior of cooling air is presented, then heat transfer performance and thermal performance of channel walls, including ribbed walls and side walls, are analyzed. The results show that the rib height, rib round radius and rib angle have great impact on heat transfer and flow of channel, while the influence of rib thickness is relatively small. Heat transfer performance and pressure penalty are positively correlated with rib height and rib angle, while negatively correlated with rib round radius. As a result, wavy ribs with high rib height and large rib round radius perform better in increasing heat transfer and decreasing pressure drop. The diversion effect of wavy ribs on cooling air is responsible for friction penalty reduction. Due to the advantages of saving space and reducing pressure loss, small rib angle is beneficial to improve the performance of wavy ribs as well. In comparison with 45° V-shaped ribs, high-performance wavy ribs induce that ribbed wall Nu/Nu0 and ribbed wall area improve by 7–37% and 28–52%, respectively, without friction loss increasing. It is indicated that the wavy rib appears to be an effective method of heat transfer improvement in internal cooling channels.

Influence of gender and body hemisphere on the occurrence of wavy ribs: An analysis of spontaneous skeletal abnormalities in Wistar rat fetuses.

The differentiation of background findings from anomalies relevant for the safety evaluation of a future drug is a major task in the interpretation of developmental toxicity studies. The anomaly wavy rib often occurs in litters exposed to the test substance, but is also frequently present in control litters. Therefore, the relevance of this finding for risk assessment is under discussion. We characterized the skeletal morphology of fetuses with wavy ribs from our background data. Differences in the incidence of wavy ribs between the genders, with approximately twice as many male fetuses having wavy ribs, compared to females, and an overrepresentation of the right body hemisphere were observed. Affected fetuses often occurred clustered in single litters. The presented data might be useful for differentiation of spontaneously occurring wavy ribs from abnormal patterns induced by a test substance.

Forced convective heat transfer and thermal efficiency assessment in square channel equipped with 10° wavy thin rib

Forced convective heat transfer and thermo-hydraulic efficiency in the heat exchanger square channel (HESC) inserted with 10° wavy thin rib (WTR) are reported numerically. The effects of rib height, pitch distance and flow velocity on flow and heat transfer profiles are considered. The rib height to the channel height; e/H or HR, is varied in the range 0.05–0.30, while the rib pitch to the channel height; P/H or PR, is varied in the range 0.50–1.25. The air velocity in the HESC inserted with the WTR is considered in terms of Reynolds number. The Reynolds numbers (Re = 100–2000) for the present investigation is analyzed at the inlet condition. The finite volume method (commercial code) with SIMPLE algorithm is picked to solve the present problem. The numerical model of the HESC inserted with the WTR is validated for both grid independence and verification of the smooth HESC. The numerical results of the HESC inserted with the WTR are printed in terms of flow and heat transfer profiles. The values of Nusselt number, friction factor and thermal efficiency factor in the HESC inserted with the WTR are also plotted. As the numerical result, it is found that the WTR in the HESC can produce the vortex flow that the reason for the enhancements of heat transfer and efficiency. The increment of the heat transfer ability in the HESC is detected when increasing rib height and Reynolds number. In addition, the greatest thermal efficiency factor in the HESC inserted with the WTR is around 3.43 at HR = 0.20, PR = 1, and Re = 2000.

Anomalies of Cartilaginous and Ossified Axial Skeleton in Rat Fetuses Treated with Cyclophosphamide: Type, Frequency, and Stage Specificity

AbstractThe purpose of the present study was to assess the type, frequency and stage specificity of axial skeletal anomalies induced by cyclophosphamide (CP). Female Crj: Wistar rats were mated with male rats (vaginal sperm = gestation day 0, GDO). They were then injected intravenously with 5 mg/kg of CP in a saline solution on GD7, 8, 9, 10, 11, 12, 13, or 14, or with saline on GD8 for controls. Dams were sacrificed on GD20. Fetuses were stained with alcian blue and alizarin red S. Eighteen types of axial skeletal anomaly were detected, e. g., shifted ventral lamina, cervical rib, cleft arch of the atlas, axis fused to atlas, sternebral misalignment, bipartite sternum, fused ribs, change in pre‐sacral vertebral number, supernumerary rib, misdirected transverse process, anteriorly‐shifted spinous process, short spinous process, fused vertebral bodies, cartilaginous short rib at Th.7, short or absent rib at Th.12 or 13, dumbbell‐shaped vertebral body, wavy rib, and rib cartilage not attached to the sternal cartilage. The present experimental study indicates that: 1) observations of cartilaginous skeletons can provide more information than observations of ossified skeletons; 2) the pattern of CP‐induced anomalies along the anterior–posterior axis may depend on the sequence of development progression among structures, spinous process, vertebral arch, vertebral body, rib/transverse process; and 3) in more cranial vertebrae, anteriorly‐shifted anomalies, such as anteriorly‐shifted ventral lamina and anteriorly‐shifted spinous processes, rather than posteriorly‐shifted anomalies, may be the primary indicators for detecting developmental toxicity, since CP injection increased the frequencies of these anomalies.

A study for effects on pre- and postnatal development, including maternal function in rats treated subcutaneously with magnesium sulfate

Magnesium sulfate, at dose levels of 250, 500 and 1000 mg/kg, was administered subcutaneously three times daily to Crj:CD(SD) female rats from day 15 through day 20 of gestation. The effects of the compound on dams and F1 animals were examined. In the dams, decreased food consumption was observed in the 500 and 1000 mg/kg groups. Hypolocomotion, pronation, bradypnea and decreased body weight gain were observed in the 1000 mg/kg group. But there were no effects on the delivery or lactation conditions and necropsy from administration of the test article. In the F1 animals, low body weight, delays in differentiation (eruption of lower incisor, opening of eyelid) and reversible change in ribs (wavy rib) were observed in the 1000 mg/kg group. But there were no effects from administration of the test article in viability, functional examinations, behavior tests or reproductive ability. Based on the above results, under the conditions of this study, it was concluded that the non-toxic dose levels for general toxicological effects on dams was 3 x 250 mg/kg/day, for reproductive ability of dams was 3 x 1000 mg/kg/day, and for development of F1 animals was 3 x 500 mg/kg/day.

Developmental Toxicity NOAEL and Postnatal Recovery in Rats Fed Boric Acid during Gestation

Boric acid (BA), an essential plant micronutrient, occurs naturally in fruits, vegetables, and other foods. It is widely used in the manufacture of glass, ceramics, and other products. In a prior study, gestational exposure to BA was associated with developmental toxicity in the rat, including fetal growth retardation and altered skeletal morphology. In order to establish the developmental toxicity no-observed-adverse-effect level (NOAEL) in the rat, BA (0, 0.025, 0.05, 0.075, 0.1, or 0.2% in feed) was administered to timed-mated rats (60/group) from gestational day (gd) 0 to gd 20. Approximately half the dams were terminated on gd 20, and the remaining dams delivered their litters. Pup growth and viability were monitored until postnatal day (pnd) 21. Dams sacrificed on gd 20 (pnd 21) ingested average doses of 0(0), 19(19), 36(37), 55(56), 76(74), or 143(145) mg BA/kg/day. Maternal clinical signs, body weight, and food and water intake were measured at regular intervals during gestation and lactation. At termination, maternal liver and right kidney were weighed, and live fetuses (gd 20) and pups (pnd 21) were weighed, sexed, and examined for morphological anomalies (external, visceral, skeletal). Maternal effects were limited to increased relative kidney weight at 0.2% BA. Viability of the offspring was unaffected. On gd 20, fetal body weight was 94 and 88% of controls at 0.1 and 0.2% BA, but recovery was complete at birth (∼gd 22). The incidence of short rib XIII was increased on gd 20 at ≥0.1% BA, but only at 0.2% on pnd 21. The incidence of wavy rib was increased on gd 20 at ≥0.1% BA, but the reversibility of this effect was confirmed on pnd 21. A slight decrease in extra lumbar ribs was observed at 0.2% BA on gd 20, and extra lumbar ribs were not found in any pups on pnd 21. Thus, the developmental toxicity NOAEL in the rat was 0.075% BA (55 mg/kg/day) on gd 20 and 0.1% BA (74 mg/kg/day) on pnd 21.

Effects of sodium bicarbonate and ammonium chloride on the incidence of furosemide‐induced fetal skeletal anomaly, wavy rib, in rats

Furosemide produces fetal wavy ribs when administered to pregnant rats during late gestation. The compound is also known to produce metabolic alkalosis in laboratory animals and man. In order to evaluate the effect of furosemide on maternal blood pH, Crj:CD(SD) female rats received an oral administration of 150 or 200 mg/kg of furosemide by gavage on day 16 of gestation and were bled at 4 hr post-dose. Compared to an average pH of 7.39 in control females, there was a significant elevation in blood pH in these furosemide-treated females (average pH of 7.44 to 7.48). When 2% sodium bicarbonate was provided in the drinking water for females treated with 150 mg/kg of furosemide, there was a further rise in maternal blood pH (7.52) compared to females treated with furosemide alone. Associated with this elevation in maternal blood pH was a marked increase in the incidence of fetal wavy ribs (87.6% compared to 27.6%). When females treated with 200 mg/kg of furosemide were provided with 0.5% ammonium chloride, furosemide-induced maternal alkalosis was corrected (pH decreased to 7.35) and there was a reduction in the incidence of fetal wavy ribs (7.0% compared to 37.2%). In addition, maternal blood pH among individual females was positively correlated with the incidence of fetal wavy ribs (r = 0.714). These results suggest that maternal metabolic alkalosis is involved in the pathogenesis of furosemide-induced wavy ribs.

The role of acoustic tube resonances in the radiation of sound from circumferentially ribbed truck tires

While in contact with the pavement surface, the grooves of circumferentially ribbed tires form tubes open at both the leading and trailing edges of the tire contact patch. These tubes efficiently radiale sound at the fundamental resonant frequency, corresponding to an acoustic wavelength equal to one half of the tube length, and at the higher harmonic frequencies. This behavior was studied with acoustic intensity measurements made alongside a moving straight rib (HCR) truck tire using the technique described in a previous presentation [L. J. Oswald and P. R. Donavan, J. Acoust. Soc. Am. Suppl. 1, 67, S71 (1980)]. These data show a 3 to 7 dB reduction from 500 to 2500 Hz in the narrow-band acoustic intensity spectrum when the resonant-tube radiation is eliminated with open cell foam placed in the grooves. Further, consistent with the dipolelike radiation from the tube ends occurring at the odd-numbered tube harmonics, distinct nulls in the acoustic intensity were measured alongside the center of the contact patch at these frequencies. The influence of resonant tube radiation is also discussed for commercial wavy rib truck and passenger car tires.

The "Wavy Rib" Syndrome

The "Wavy Rib" Syndrome