Rib Case Research Articles

The influence of wall roughness on bubble drag reduction in Taylor–Couette turbulence

We experimentally study the influence of wall roughness on bubble drag reduction in turbulent Taylor–Couette flow, i.e. the flow between two concentric, independently rotating cylinders. We measure the drag in the system for the cases with and without air, and add roughness by installing transverse ribs on either one or both of the cylinders. For the smooth-wall case (no ribs) and the case of ribs on the inner cylinder only, we observe strong drag reduction up to DR$=33\,\%$ and DR$=23\,\%$, respectively, for a void fraction of $\unicode[STIX]{x1D6FC}=6\,\%$. However, with ribs mounted on both cylinders or on the outer cylinder only, the drag reduction is weak, less than DR$=11\,\%$, and thus quite close to the trivial effect of reduced effective density. Flow visualizations show that stable turbulent Taylor vortices – large-scale vortical structures – are induced in these two cases, i.e. the cases with ribs on the outer cylinder. These strong secondary flows move the bubbles away from the boundary layer, making the bubbles less effective than what had previously been observed for the smooth-wall case. Measurements with counter-rotating smooth cylinders, a regime in which pronounced Taylor rolls are also induced, confirm that it is really the Taylor vortices that weaken the bubble drag reduction mechanism. Our findings show that, although bubble drag reduction can indeed be effective for smooth walls, its effect can be spoiled by e.g. biofouling and omnipresent wall roughness, as the roughness can induce strong secondary flows.

Experimental and numerical study on the effects of rib orientation angle on film cooling performance of compound angle holes

To investigate the effects of the inclined ribs on internal flow structure in film hole and the film cooling performance on outer surface, experimental and numerical studies are conducted on the effects of rib orientation angle on film cooling of compound angle holes. Three coolant channel cases, including two ribbed cross-flow channels (135° and 45° inclined ribs) and the plenum case, are studied for three blowing ratios. The 2D contours of film cooling effectiveness and heat transfer coefficient are measured by transient liquid crystal measurement technique. The steady RANS simulations with realizable k-ε turbulence model and enhanced wall treatment are performed. The results show that the lateral spread of the coolant jet on the surface is paramount influenced by the rib orientation angle. The lateral spread of the 45° rib case is obviously larger than that of the 135° rib case for lower blowing ratios. For the blowing ratio of 1.0, the area-averaged cooling effectiveness for the 135 and 45° rib angles is higher by a factor of 38% and 107%, respectively, compared to the plenum case. With the increase of blowing ratio, the film coverage difference becomes smaller between different rib orientation cases. The 45° rib case also produces a higher heat transfer coefficient, which is higher than the 135° rib case by 3.4–8.7% within the studied blowing ratio range. The discharge coefficient of the 45° rib case is the lowest among the three cases. The helical motion of coolant flow is observed in the hole of the 45° rib case. The jet divides into two parts after ejecting out of the hole due to this motion, which results in the strong velocity separation and loss. For the 135° rib case, the vortex in the upper half region of the secondary-flow channel rotates in the same direction with the hole inclination direction, which leads to the straight streamlines and thus results in lower loss and higher discharge coefficient.

Enhancement of cooling performance of a helium-cooled divertor through the addition of rib structures on the jet-impingement area

The development of nuclear fusion, which is an environmentally friendly and future-oriented power generation method, needs to be developed for the prevention of global warming caused by the excessive use of fossil fuels. However, there are many scientific and technical challenges that should be overcome for the use of nuclear fusion reactors. The development of a divertor is one such challenge, in that it should be able to endure a high heat flux (∼10 MW/m2) and a particle flux (∼1024/s). To solve this challenge, the Karlsruhe Institute Technology (KIT) has been developing a helium-cooled divertor with a multi-array impingement jet. The main objective of developing this divertor module is not only to sufficiently dissipate the high thermal load from plasma for a reliable operation, but also to maintain a moderate pressure drop. To achieve this objective, we should understand the heat transfer characteristics of the divertor module and enhance the thermal performance, namely, the thermal conductance and pressure drop. The present study is aimed at an enhancement of the cooling performance of a helium-cooled divertor through the addition of rib structures in the divertor module. The results show that the convective conductance with rib turbulators is increased through an increase in the interfacial area on a heated surface. In addition, the thermal performance of the divertor module is enhanced by 20% or more compared with a no rib case.

Effect of rib orientation on thermal and fluid-flow features in a two-pass parallelogram channel with abrupt entrance

Detailed secondary flow patterns, Nusselt number (Nu) distributions, Fanning friction factor (f), and thermal performance factor (TPF) are compared between three different rib orientations (45-deg, −45-deg, and 90-deg) in a stationary two-pass parallelogram channel with an asymmetrically and suddenly contracted inlet condition. Velocity and temperature measurements are performed with Particle Image Velocimetry (PIV) and Infrared Thermometry (IT). Temperature and pressure drop measurements are conducted under Reynolds number (Re) ranging from 5000 to 20,000, while the velocity measurements are carried out at fixed Re=10,000. A cross-sectional equal length, 45.5mm, of adjacent sides is selected and two pairs of opposite angles are 45-deg and 135-deg. The rib-height to channel-height ratio and rib pitch-to-height ratio are 0.1 and 10, respectively. It is found that the combined effect of inlet condition and rib orientation extends to whole parallelogram channel rather than the first passage only. Among the rib orientations investigated, the 45-deg ribs strengthen the effects of parallelogram slant sidewalls and entrance and further widen the Nu difference between top and bottom walls. In contrast, the other two rib configurations, 90-deg ribs especially, weaken these effects and narrow the corresponding differences. Based on the ability to elevate the surface-averaged Nu0‾/Nu∞ ratio, the orders (45-deg, −45-deg, 90-deg) and (90-deg, 45-deg, −45-deg) respectively for present top and bottom walls are significantly distinct from those in square and rectangular channels. The variations of channel-averaged Nu0‾/Nu∞ and f0‾/f∞ with the associated TPF values against Re are plotted and compared with previous results obtained from literature. Overall speaking, three tested angled ribs all provide the TPF values above than unity; however, only the TPF values in 45-deg case are always higher than those in corresponding smooth parallelogram channel (ASI case). Divided by the TPF values in ASI case, the normalized TPF values are respectively 1.09–1.04, 1.07–0.87, and 0.83–0.99 for 45-deg, 90-deg, −45-deg ribbed cases. It is thus important to take the entrance effect into account when applying the angled ribs in a two-pass parallelogram channel.

Investigation on the effects of rib orientation angle on the film cooling with ribbed cross-flow coolant channel

To evaluate the application of ribs in gas turbine blade cooling better, particularly the influence on internal cooling of the film hole effusion and how the internal flows effect the film cooling, this paper presents the effects of rib orientation angle on the film cooling performance. Experimental and numerical studies are conducted on the film cooling with different coolant channel structures. Three coolant channel configurations, including the plenum case and two ribbed cross-flow channels (135° and 45° angled ribs) under three blowing ratios (0.5, 1.0 and 2.0), are considered. The Reynolds numbers of mainstream and coolant channel are fixed as 104 and 105, respectively. Film cooling performances are measured under three blowing ratios by transient liquid crystal measurement technique. Reynolds-averaged Navier-Stokes (RANS) simulation with realizable k-ε turbulence model and enhanced wall treatment are performed using a commercial code Fluent. Under lower blowing ratios, the film jets have better coverage and higher cooling effectiveness. The cases with different ribbed cross-flow channels provide different cooling effectiveness and significantly outperform the plenum case. Based on the results of the plenum case, the superiority regarding area averaged film cooling effectiveness of 135° rib case and 45° rib case are 50% and 16%, respectively. Under the blowing ratio is 1.0, the cases with ribbed cross-flow coolant channels exhibit 170% higher film cooling effectiveness relative to the plenum cases. The film lifts off from the wall surface which results in low film cooling effectiveness in the region near the film hole under higher blowing ratio. The 135° rib case also performs higher cooling effectiveness. Further, heat transfer coefficient of 135° rib case is inferior to the plenum case, showing an inferiority of 0.7–1.6% under lower blowing ratio. However, the superiority regarding area averaged heat transfer coefficient of 45° rib case is 5.0–12.4% with the blowing ratio increasing from 0.5 to 2.0. The discharge coefficient of the 45° rib case is lowest among the three cases. The helical motion of secondary flow is observed in the hole of 45° rib case. The jet divides into two parts after being blown out of the hole due to this motion, which induces strong velocity separation and loss. In the 135° rib case, the vortex in the upper half region of the secondary flow channel rotates in the same direction with the hole inclination direction which leads to the straight streamlines and thus results in lower loss and higher discharge coefficient.

Large-eddy simulation of turbulent flow and structures in a square duct roughened with perpendicular and V-shaped ribs

In this paper, highly disturbed turbulent flows confined within a square duct with uniformly spaced V-shaped ribs mounted on one wall are investigated using large-eddy simulation (LES). Two V-shaped (60° and 45°) rib cases are studied in comparison with the perpendicular (90°) rib case. The LES results are validated against a set of water-channel measurement data newly acquired by the authors. The effects of different shaped ribs on turbulent flow are systematically studied in terms of the mean velocity field, turbulence statistics, and coherent structures. The results show that strong secondary flows in the pattern of a pair of large symmetrical streamwise-elongated vortices exist in all three rib cases. The impacts of rib geometry on turbulent coherent structures are investigated using vortex identifiers, temporal autocorrections, spatial two-point autocorrelations, and velocity spectra.

Chest wall reconstruction using steel wire in a case of Chondrosarcoma Rib: a novel technique of neo-rib

Chest wall tumor usually requires enbloc resection of tumor with overlying skin, adjoining ribs, and occasionally sternum. An ideal prosthetic material to cover the bony defect as well as maintain respiratory mechanics is yet to be developed. Commonly available methods include combination of the mesh with rigid metallic plates, bone cement, etc., over the skeletal defect, which is then covered with a muscle flap. Here, we are reporting a case of Chondrosarcoma Rib in which rib was reconstructed using non-rigid stainless steel wire, which is easily available and simple to perform.

Two cases of bifid ribs observed in the fourth and the fifth rib

Two cases of bifid ribs observed in the fourth and the fifth rib

Film cooling performance and flow characteristics of internal cooling channels with continuous/truncated ribs

To better evaluate the application of ribs in gas turbine blade cooling, this numerical study reports on the effects of ribs mounted on the internal cooling channel wall on external adiabatic film cooling performance. The numerical model is validated against available experimental data. For fixed mainstream and cooling flow Reynolds numbers, three ribs including the continuous rib, centrally truncated rib and laterally truncated rib at two blowing ratios (i.e., 0.5 and 1.0) are considered. At lower blowing ratio, results show that the cases with three distinct ribs provide approximately identical cooling effectiveness but significantly outperform the case without ribs. The superiority regarding laterally averaged adiabatic cooling effectiveness is 17–157%. However, at higher blowing ratio, the cases with ribs are inferior to the case without ribs, showing an inferiority of 21–68%. Further, at higher blowing ratio, the case with continuous ribs exhibits a 12–45% higher localized cooling effectiveness relative to other ribbed cases. It is found that cooling effectiveness deteriorates with the increase of spiral intensity of the coolant flow inside the film hole. Lower spiral intensity leads to a better covering of target wall by the coolant and thus results in better cooling effectiveness. The distinct relative merits among the cases at different blowing ratios are explored based on the aforementioned dominant mechanism.

Experimental investigation of impingement heat transfer from a round rib-roughened surface

An experimental investigation on impingement heat transfer from a rib-roughened surface is performed. Single, double, and triple rib configurations are tested. The rib is also located at three different positions for a single rib case. The Reynolds number is varied from 10,000 to 50,000 whereas the dimensionless jet-to-surface distance (z/D) is kept constant as 8. Results show that, the Nusselt number decreases just before a rib. After the rib, however, the Nusselt number decreases by a larger amount. Since ribs cause a reincreasing in the Nusselt number after the stagnation point and since the stagnation point Nusselt number is not affected by ribs, they can be used to enhance heat transfer especially for spot cooling applications. It is also obtained that using ribs is more useful for low speed impinging jets, when heat transfer from the whole surface is considered.

A case of bifid rib: Presentation and complications

A case of bifid rib: Presentation and complications

Investigation of particle deposition efficiency enhancement in turbulent duct air flow by surface ribs with hybrid-size ribs

This study presents the particle deposition enhancement by hybrid-size and same-size surface ribs in turbulent air duct flows using computational fluid dynamics simulation. The Reynolds stress turbulence model with UDF corrections and discrete particle model were adopted to simulate the turbulent air flow fields and particle deposition behaviours, respectively. After numerical validation with the relative literature results, pure particle deposition enhancement ratios, flow drag increase, comprehensive deposition efficiency and deposition enhancement mechanisms were investigated and discussed in details. The findings showed that the hybrid-size ribs with small rib spacing have the best enhancement performance on particle deposition for small particles ([Formula: see text]). Considering the flow drag increase, the maximum deposition efficiency can reach 485 for 1 µm particles for the hybrid-size ribbed cases, while it is just 425 for the same-size ribbed case. Nevertheless, no obvious particle deposition enhancement can be found for large particles ([Formula: see text]) for all types of surface ribs. The hybrid-size surface ribs are more efficient compared with the same-size ribs, which can be applied in the air cleaning equipment to improve the aerosol particle removal performance.

Prevalence and pattern of cervical rib, transversomegaly and other vertebral anomalies in normal adult cervical spine in Kumaon region of Uttarakhand, India

<p class="abstract"><strong>Background:</strong> A supernumary rib from seventh cervical vertebra is called cervical rib and is a common anomaly. Its true prevalence is not validated as most of these are asymptomatic thus do not get diagnosed. Its incidence has been reported in several geographic regions and ethnic clusters. Most of the studies rely on radiological data collected from evaluation of chest or neck radiographs of defined numbers.</p><p class="abstract"><strong>Methods:</strong> A similar study to ascertain its presence and incidence, apart from sexual and morphological pattern is required for Kumaon region of Uttarakhand, India. The present study reports data extracted from study of 1500 radiographs and evaluating them for presence of cervical rib and other abnormalities. Demographic and other relevant details were noted.<strong></strong></p><p class="abstract"><strong>Results:</strong> Most of the cases were female and almost all cases of cervical rib or transversomegaly were bilateral. 0.8% and 1.4% cases were noted for cervical rib and transversomegaly respectively. Apart from it, 4 cases of vertebrae fusion and one case of hemi-vertebra leading to cervical scoliosis was also noted.</p><strong>Conclusions:</strong> The prevalence of cervical rib was comparable to other studies considering the sample size. The calculation of true incidence however will require multi-discipline collaboration and robust data. This study, however, is important for further work in this regard and adds value to existing literature.

Value of imaging in the diagnosing echinococcosis of ribs

Objective To investigate the imaging features of CT and MRI of echinococcosis, and improve the imaging knowledge of the disease. Methods Clinical and radiological findings of echinococcosis of ribs were retrospectively analyzed by reviewing the seventeen cases confirmed by clinical and pathological findings. All patients had CT scan, eight had X-ray plain film and five had MR examination, while 4 patients underwent additional contrast-enhanced CT examination. Results All lesions were unilateral. There were 33 ribs involved, and single involved rib was seen in 7 cases. On CT scans, 10 cases showed cystic, swelling and osteolytic bone destruction, and 7 cases showed moth-eaten osteolytic bone destruction. There were 13 cases of hydatid cyst, 3 cases of a single sac watery density shadow and 10 cases of polycystic separating wheels form. There were 4 cases of fractured ribs, 2 cases of the longitudinal fracture and 2 cases of the transverse fracture. On MRI, there was one case of rib medullary cavity expansion destruction. It was a single cyst with hypointensity on T1WI, hyperintensity on T2WI and hyperintensity on short time inversion recovery (STIR) images. There were one case of rib medullary cavity expansion destruction and 3 cases of hydatid erosion ribs cortex among 4 cases of polycystic type. Polycystic type echinococcosis appeared hypointensity on T1WI, hyperintensity on T2WI and hyperintensity on STIR images. Polycystic type had mother sac and ascus structure, and signal intensity of ascus was higher. STIR sequence showed more clearly polycystic structure. Conclusions CT and MRI can clearly show location of echinococcosis of ribs. There are the imaging features of cystic, swelling and osteolytic bone destruction or complicating cyst of polycystic type which can help the qualitative diagnosis of rib echinococcosis. Key words: Ribs; Echinococcosis; Tomography, X-Ray computed; Magnetic resonance imaging

Flow characteristics of an offset jet over a surface mounted square rib

ABSTRACTA three-dimensional offset jet flow over a surface mounted square rib was investigated using particle image velocimetry at Reynolds number of 7600. The square rib was mounted at three different locations downstream of the nozzle exit. Contour and profile plots in the symmetry plane were used to investigate the effect of the rib on the mean flow distribution and turbulence statistics. Changing the rib location enhanced the mixing and entrainment characteristics of the jet thereby leading to larger wall-normal spread rates. The quadrant analysis revealed a significant contribution of all events towards the Reynolds shear stress. The joint probability density function analysis showed that the structures within the outer shear layer of the jet differed from those of boundary layers. Results from the two-point correlation analysis indicated that the introduction of a surface mounted rib modified the flow structures within the developing region. However, there was no significant structural difference between the flow with mounted rib and the no rib case within the self-similar region. The proper orthogonal decomposition was used to examine how changes in rib location modified the dynamics of the energetic modes towards the turbulent kinetic energy and Reynolds shear stress within the developing and self-similar regions.

Thoracic Facet Arthropathy Presenting with Pain Abdomen: An Unusual Presentation

This case report is about a patient with thoracic facet arthropathy presenting with abdominal pain, who underwent multiple investigations and treatment for abdominal visceral conditions with no relief of his pain. A 29 years male presented to our pain clinic with episodic, severe left chest wall, and upper abdominal pain. In the last 4 years, he had been treated for various abdominal visceral conditions. He was then diagnosed as a case of intercostal neuralgia and 12th rib (the twelfth rib syndrome). He was treated with anticonvulsants and antidepressants, as well as intercostal nerve block, tender point injection and intercostal nerve radiofrequency (RF), but with partial relief. Careful history and clinical examination revealed left lower thoracic facet joint involvement. Diagnostic block of medial branch of left 10, 11 and 12th thoracic dorsal rami was done with 90% pain relief. This case emphasises that in any case of abdominal pain, spine should be examined because referred pain from spine can be an important etiology of pain abdomen. Careful history, examination and appropriate investigations should be done to rule out abdominal pathologies, and to arrive at a diagnosis. A thorough history, meticulous examination, and diagnostic blocks if required are very important to localize the pain generators.

Highly-disturbed turbulent flow in a square channel with V-shaped ribs on one wall

We investigate highly-disturbed turbulent flows in a square channel with V-shaped ribs mounted on one wall. A planar particle image velocimetry (PIV) system is used to measure the fully developed turbulent flow at the channel midspan and two off-center planes. V-shaped rib configurations with three different inclinations (60°, 45° and 30°) are studied and compared to the perpendicular (90°) rib case. The highly-disturbed turbulent flow in the V-shaped rib cases are studied by investigating the statistics of first and second order moments, including the mean velocity, mean shear, mean vorticity and Reynolds stresses. Owing to the geometrical skewness of the V-shaped ribs, strong secondary flows are induced which appear in the pattern of a pair of streamwise counter-rotating roll cells and have a significant impact on the momentum transport process. Near the channel midspan of the V-shaped ribs, turbulent intensity is suppressed above the ribs but enhanced below the rib height, and turbulent vortical motions exhibit isotropic patterns due to the strong disturbances from the ribs. The coherent flow structures have been systematically analyzed based on studying two-point auto-correlation coefficient, quadrant decomposition of Reynolds stresses, swirling strength, and proper orthogonal decomposition of the turbulent flow.

Experimental investigation of the effect of variously-shaped ribs on local heat transfer on the outer wall of the turning portion of a U-channel inside solar air heater

In the present work, an experimental investigation of convective heat transfer and pressure drop was carried out for the turning portion of a U-channel where the outer wall was equipped with ribs. The shape of the ribs was varied. The investigation aims to give guidelines for improving the thermo-hydraulic performance of a solar air heater at the turning portion of a U-channel. Both the U-channel and the ribs were made in acrylic material to allow optical access for measuring the surface temperature by using a high-resolution technique based on narrow band thermochromic liquid crystals (TLC R35C5 W) and a CCD camera placed to face the turning portion of the U-channel. The uncertainties were estimated to 5 and 7 % for the Nusselt number and friction factor, respectively. The pressure drop was approximately the same for all the considered shapes of the ribs while the dimpled rib case gave the highest heat transfer coefficient while the grooved rib presented the highest performance index.

Cervical Rib Causing Occlusion of the Subclavian Artery and Thoracic Outlet Syndrome

Purpose: To present an unusual case of a cervical rib as a cause of subclavian artery occlusion and thoracic outlet syndrome. Procedures: Case report Results: A 39-year-old female presented to the emergency room with a 2-day history of unilateral headache, facial tingling, and slurred speech, along with a 2-month history of left upper extremity weakness and coolness of the left hand. A stroke workup that included carotid duplex ultrasonography revealed findings suggestive of left subclavian occlusion, later confirmed on CT angiography. Neurologic workup suggested migraine, rather than ischemia, as the cause of headache; however, the subclavian occlusion prompted further investigation, including a chest radiograph that revealed bilateral cervical ribs. The patient was taken to surgery where her left cervical rib was excised and the chronically occluded left subclavian artery was found to have significant post-stenotic dilatation. Given that the chronic nature of her left upper extremity symptoms were not limiting, the decision was made to not undertake bypass. Recommendation was made to remove her right cervical rib prophylactically at a future date. Conclusions: Cervical ribs are a rare cause of vascular thoracic outlet syndrome, with compression leading to post-stenotic dilatation and symptoms of ischemia in the involved extremity.

Bifid rib: A rare anomaly

A case of the bifid rib was found during routine bone study. The distal part of the osseous rib bifurcated into two divisions with an angle of 60°. Both divisions had their own costal cartilage. Bifid rib is a congenital abnormality of the rib cage and usually asymptomatic, often discovered incidentally on chest X-ray. Effects of this neuroskeletal anomaly can include respiratory difficulties and neurological limitations.