Fluctuating Characteristics of the Stilling Basin with a Negative Step Based on Hilbert-Huang Transform

The violent fluctuation of hydrodynamic pressure in stilling basins is an important factor threatening the safety of the bottom plates of stilling basins, and plays an important role in the safe operation of stilling basins. In order to deeply understand the fluctuating characteristics of stilling basins, the fluctuating pressure signal of a stilling basin bottom plate is processed by the Hilbert-Huang transform method through a hydraulic model test. In this paper, three signal decomposition methods are used to decompose the pulsating pressure signal. A Hilbert transform is used to select the component with the best decomposition effect. The time-frequency-amplitude diagram of the pulsating pressure signal is obtained by Hilbert transform, and its time-frequency characteristics are discussed in depth. The analysis results are as follows: (a) the decomposition results from the CEEMD method are orthogonal and complete. The HHT method is suitable for processing fluctuating pressure signals. (b) With an increase in IMF decomposition order, the signal frequency band becomes narrow, the Hilbert spectrum amplitude decreases and the pulsating pressure energy decreases. The decomposition of the fluctuating pressure signal into components of different scales shows that the turbulence is composed of multiple scales of vortices, reflecting the vortex structure in the turbulence. (c) The jet impingement zone of the drop bucket stilling basin is near x/L = 0.075. The dominant frequency and marginal spectrum energy of the jet impingement zone are very prominent, and the marginal spectrum energy is mostly concentrated within 5.0 Hz. (d) At different drop height and different flow energy ratio, the fluctuation in the dominant frequency of fluctuating pressure decreases, the dominant frequency of the head of the stilling basin is larger, the dominant frequency of the middle and rear parts tends to be stable, and the dominant frequency is finally stabilized at about 1.0 Hz. This paper attempts to use the HHT method to process the fluctuating pressure signal, and the results provide a new discussion method for exploring the fluctuating pressure characteristics of hydraulic structures.

Genes associated with inflammation and bone remodeling are highly expressed in the bone of patients with the early-stage cam-type femoroacetabular impingement

Background Recent studies have shown high expression levels of certain inflammatory, anabolic, and catabolic genes in the articular cartilage from the impingement zone of the hips with femoroacetabular impingement (FAI), representing an increased metabolic state. Nevertheless, little is known about the molecular properties of bone tissue from the impingement zone of hips with FAI. Methods Bone tissue samples from patients with early-stage cam-type FAI were collected during hip arthroscopy for treatment of cam-type FAI. Control bone tissue samples were collected from six patients who underwent total hip replacement because of a femoral neck fracture. Quantitative real-time polymerase chain reaction (PCR) was performed to determine the gene expression associated with inflammation and bone remodeling. The differences in the gene expression in bone tissues from the patients with early-stage cam-type FAI were also evaluated based on clinical parameters. Results In all, 12 patients with early-stage cam-type FAI and six patients in the control group were included in this study. Compared to the control samples, the bone tissue samples from patients with FAI showed higher expression levels of interleukin-6 (IL-6), alkaline phosphatase (ALP), receptor activator of nuclear factor-kB ligand (RANKL), and osteoprotegerin (OPG) (P < 0.05). IL-1 expression was detected only in the control group. On the other hand, there was no significant difference in IL-8 expression between the patients with FAI and the control group. The patients with FAI having a body mass index (BMI) of >24 kg/m2 showed higher ALP expression (P < 0.05). Further, the expression of IL-6 and ALP was higher in the patients with FAI in whom the lateral center-edge angle was >30° (P < 0.05). Conclusions Our results indicated the metabolic condition of bone tissues in patients with early-stage cam-type FAI differed from that of normal bone in the femoral head-neck junction. The expression levels of the genes associated with inflammation and bone remodeling were higher in the bone tissue of patients with early-stage cam-type FAI than in the patients with normal bone tissue.

Near-Wall Velocimetry in the Impingement-Zone of a Micro-Droplet and a Round Jet Stream

Near-wall fluid velocimetry in the impingement zone of a micro-droplet stream on a flat surface is reported utilizing micro-Particle Tracking Velocimetry . The results are then compared with the near-wall fluid velocimetry in the impingement region of a steady micro-jet stream. The presence of tracer particles in the fluid results in a small movement of the droplets away from the orifice axis, causing a change in the location of the droplet impingement center. A new method to find the center of impingement is described, and an algorithm is developed to obtain the radial velocities in the impingement zone at three out-of-plane heights of 2µm, 7µm, and 10±2µm from the wall. Single-frame double-exposed images of fluorescent tracer particles at low loading are used for the experiments. As the impingement frequency of the droplet stream is much higher than the image-capturing rate of the camera, each double-exposed image corresponds to a different random instance within the impingement period of the droplets. The presented results show the occurrence of a higher normalized root mean square along with positive skewness of the measured radial velocity values for the droplet stream. These indicate higher velocity fluctuations or fluid mixing characteristics induced by the droplet-crown propagation for the droplet stream when compared to that of a jet stream. The near-wall velocity measurements support previously reported observations of the enhanced convection heat transfer characteristics for a droplet stream case.

Characterization of Transient Wall Heat Load for a Low NOx Lean Premixed Swirl Stabilized Can Combustor Under Reacting Conditions

Modern combustor design optimization is contingent on the accurate characterization of the combustor flame side heat loads. Knowledge of regions of high and low heat loads on the liner wall helps designers optimize the cooling designs. The present work focuses on the experimental measurement of the transient heat load along a fused silica (quartz) optical can combustor under reacting conditions for a swirl stabilized premixed methane-air flame. Equivalence ratio was varied from 0.55 to 0.65. Reynolds number based on combustor diameter was varied from 12500 to 18000, where the preheated air temperature was approximately 373 K. The percentage of pilot fuel was varied from 6% to 10% of the main fuel flow rate. Inner and outer walls of the liner were painted with a high temperature flat black paint with an azimuthal offset to aid in infrared measurement of the wall temperature using an infrared camera. Particle Image Velocimetry (PIV) was employed to visualize the flow field for various reacting conditions studied in this work. Based on the heat transfer study, a detailed report of transient heat load along the length of the liner wall for varying reacting conditions has been presented here. The location of impingement of the flame onto the liner and velocity of the flow field were obtained from PIV measurements. Wall heat load at various planes along the length of the liner have been presented. Repeatability of this transient experiment was within 10% between eight different runs for various locations along the length of the liner, except for the region close to flame impingement zone. In the impingement zone, liner heat load varied by about 25% between different runs. It was observed that the change in heat load upstream of the location of impingement on the liner was insignificant with change in pilot ratio as the system tends towards a steady state, contrary to the regions downstream. Higher Reynolds number and equivalence ratios increased the heat load on the liner as expected.

Intraarticular Inflammation and Catabolic Markers in Femoroacetabular Impingement during Progression of Disease -comparison between early and late stage disease-

Objectives: Femoroacetabular impingement (FAI) has been proposed as an etiologic factor in up to 50% of osteoarthritis hips (OA). Inflammation is thought to be one of the main initiators of hip OA, yet little is known about the location and progression of intraarticular inflammation in FAI hips. The aim of this study is to characterize inflammation and catabolic markers in the early and late stage of FAI hips in patients with symptomatic Cam FAI. Methods: Head-neck cartilage, acetabular cartilage, and synovial samples were obtained from 30 patients undergoing hip surgery. Fifteen patients had a diagnosis of symptomatic Cam FAI (early FAI-symptomatic FAI) and 15 presented with advanced OA secondary to Cam FAI (late FAI/secondary OA). Control cartilage samples were procured from the head-neck junction of 7 osteochondral fresh allografts from healthy young-adult donors (control). Radiographically, the α-angle was utilized to confirm hip impingement and Tönnis grade was used to define pre-OA (Tönnis grade 0-1) and advanced OA (Tönnis grade >2). Safranin O stained sections were used to assess cartilage degeneration using the Mankin score. Immunostaining of IL-1β, MMP-13, ADAMTS-4, type II collagen (COL2), and the NITEGE aggrecan neoepitote was performed to evaluate inflammation and catabolic markers. Quantification of immunopositive cells was performed and one-way analysis of variance with Tukey’s post hoc test was applied to analyze differences between groups. Results: Characteristics of the study participants are presented in Table 1. Cartilage from the impingement zone (head-neck and acetabulum) of hips with early and late FAI showed microscopic osteoarthritic degenerative changes. Compared to control, head-neck cartilage from early and late stage FAI hips highly expressed inflammatory and catabolic markers IL-1β (69.7±18.1, 72.5±13.2 vs 20.2±4.9), MMP-13 (79.6±12.6, 71.4±18.8 vs 25.3±9.5), ADAMTS-4 (83.9±12.2, 82.6±12.5 vs 24.3±11.1), NITEGE (89.7±7.7, 95.7±4.7 vs 39.8±20.5) (p<0.05). Expression for COL2 was similar among groups (93.6±3.9, 92.5±5.8 vs 95.4±6.4, p=0.4892). Finally, percent of immunopositive cells for IL-1β, MMP-13, ADAMTS-4, and ACAN were positively correlated with Mankin score (r=0.52-0.75; p<0.001). The percentage of immunopositive cells present in acetabular cartilage was similar in both early and late FAI (IL-1β: 83.3 ± 24.8, 80.7 ± 15.6, 80.9 ± 26.3, p = 0.9571; MMP-13: 94.3 ± 9.7, 85.2 ± 12.3, 93.3 ± 10.3, p = 0.0653; ADAMTS-4: 98.5 ± 2.3, 98.4 ± 3.4, 99.2 ± 3.0, p = 0.6997, COL2: 99.8 ± 0.7, 99.7 ± 1.1, 98.6 ± 3.6, p = 0.3830). Additionally, inflammatory and catabolic markers were secreted to the ECM (extracellular matrix) in late FAI but not in early FAI. (Figure 1) Synovitis was minimal in early FAI but severe in late FAI. The average synovitis score was lower in early FAI than late FAI (2.5 ± 1.7, 4.4 ± 1.6; p=0.0086). Lower IL-1β expression levels were noted in synovium from early FAI compared to late FAI (p=0.001). Conclusion: Osteoarthritic degenerative changes, inflammation and catabolic markers are evident in the cartilage from the head-neck and acetabulum (impingement zone) in patients with hip FAI morphology during early and late stage disease. In late disease, increase expression of these markers are also observed in the ECM. Severe synovitis, however, was only evident in late stage disease. This study defines joint specific location and timing of inflammation relative to the disease process, suggesting the impingement area is a potential mediator of inflammation and joint degeneration during disease progression.

Inflammatory Response of Articular Cartilage to Femoroacetabular Impingement in the Hip

Background: Femoroacetabular impingement (FAI) has been proposed as an etiologic factor in up to 50% of hips with osteoarthritis (OA). Inflammation is thought to be one of the main initiators of OA, yet little is known about the origin of intra-articular inflammation in FAI hips. Hypothesis: Articular cartilage from the impingement zone of patients with FAI has high levels of inflammation, reflecting initial inflammatory process in the hip. Study Design: Controlled laboratory study. Methods: Head-neck cartilage samples were obtained from patients with cam FAI (cam FAI, early FAI; n = 15), advanced OA secondary to cam FAI (FAI OA, late FAI; n = 15), and advanced OA secondary to developmental dysplasia of the hip (DDH OA, no impingement; n = 15). Cartilage procured from young adult donors (n = 7) served as control. Safranin O–stained sections were assessed for cartilage abnormality. Tissue viability was detected by TUNEL assay. Immunostaining of interleukin 1β (IL-1β), catabolic markers (matrix metalloproteinase 13 [MMP-13], a disintegrin and metalloproteinase with thrombospondin motif 4 [ADAMTS-4], aggrecan antibody to C-terminal neoepitope [NITEGE]), and an anabolic marker (type II collagen [COL2]) was performed to evaluate molecular inflammation and metabolic activity. The average percentage of immunopositive cells from the total cell count was calculated. Kruskal-Wallis test followed by Steel-Dwass post hoc test was used for multiple comparisons. Results: Microscopic osteoarthritic changes were more prevalent in cartilage of cam FAI and FAI OA groups compared with DDH OA and control groups. Cartilage in cam FAI and FAI OA groups, versus the DDH group, had higher expression of inflammatory molecules IL-1β (69.7% ± 18.1% and 72.5% ± 13.2% vs 32.7% ± 14.4%, respectively), MMP-13 (79.6% ± 12.6% and 71.4% ± 18.8% vs 38. 5% ± 13.3%), ADAMTS-4 (83.9% ± 12.2% and 82.6% ± 12.5% vs 45.7% ± 15.5%), and COL2 (93.6% ± 3.9% and 92.5% ± 5.8% vs 53.3% ± 21.0%) ( P < .001). Expression of NITEGE was similar among groups (cam FAI, 89.7% ± 7.7%; FAI OA, 95.7% ± 4.7%; DDH OA, 93.9% ± 5.2%; P = .0742). The control group had minimal expression of inflammatory markers. Inflammatory markers were expressed in all cartilage zones of early and late FAI but only in the superficial zone of the no impingement group. Conclusion: Cartilage from the impingement zone in FAI is associated with a high expression of inflammatory markers, extending throughout all cartilage zones. Clinical Relevance: Inflammation associated with FAI likely has a deleterious effect on joint homeostasis. Further clinical and translational studies are warranted to assess whether and how surgical treatment of FAI reduces molecular inflammation.

Anteromedial Labral Tears: Surgical Prevalence and Relationship with Chondral Damage of the Hip

Structural abnormalities of the hip joint have been identified as a common cause of labral and chondral lesions of the hip joint. However, labral and chondral damage can occur in the absence of structural abnormalities. The authors examined the incidence of anteromedial (AM) labral lesions, occurring in a nonimpinging region of the hip joint, and determined if the prevalence and location of concomitant chondral lesions differ between patients with AM lesions and those without. Between 2001 and 2013, they assessed 2,080 hips (1,818 patients) undergoing hip arthroscopy for the presence of AM labral lesions (between 4 and 6 o'clock position) and documented incidence of these lesions. The articular cartilage of the posterior, superior, and anterior regions of the acetabulum and femoral head was assessed. The degree of damage was classified as absent, mild (grades I/II), or severe (grades III/IV). The prevalence and severity of lesions in each region were compared between patients with AM lesions and those without. The authors identified 1,140 hips (1,028 patients) (55%) with labral tears in the AM region of the acetabulum. The cohort consisted of 689 females and 328 males, with an average age of 37.9 ± 12 years. Chondral lesions were present in all regions of the femoral head and acetabulum in both patients with AM lesions and those without. There is a relationship between the presence of AM lesion and prevalence of chondral lesions in the posterior and anterior femoral head and acetabulum, with a higher prevalence of lesions observed in patients without AM tears. Their findings show that lesions in the AM region of the acetabular labrum can occur with high prevalence in patients. These lesions are often associated with concomitant injuries to the anterior chondral surfaces, which may differ from lesions in the impingement zone. A thorough evaluation of all regions of the hip joint is warranted during arthroscopy to identify and treat all potential lesions.

Experimental and Numerical Visualization of Heat Transfer and Hydrodynamics Induced by Double Droplet Train Impingement

The objective of this study was to visualize and simulate the thermal physical process during double droplet train impingement for three different horizontal impact spacings (S = 0.65 mm, 1.2 mm and 2 mm). Two identical HFE-7100 droplet trains were produced using a piezoelectric droplet generator at a frequency of 6000 Hz with a corresponding droplet Weber number of 312. A translucent sapphire substrate with a thin film ITO coating was used as heater in the experiments. The heat transfer and hydrodynamics of double droplet train impingement have been visualized using IR thermal imaging and high speed optical imaging techniques, respectively. The double droplet train impingement process was also simulated numerically using the Coupled Level Set-Volume of Fluid (CLS-VOF) approach with dynamic mesh adaption (DMA). Humps were observed both numerically and experimentally between two adjacent impact craters due to the interactions caused by the impinging droplet trains. It was found that the hump height decreased when impact spacing increased. IR images show that higher impact spacing leads to better heat transfer performance, which could be due to the lower hump height at greater impact spacing conditions. It was also observed that higher impact spacing leads to better thermo-hydrodynamics within and outside the impingement zone. In summary, results show that horizontal impact spacing plays a significant role in double droplet train impingement cooling. This work was supported by the National Priority Research Program of the Qatar National Research Fund, Grant No.: NPRP 6-1304-2-525.