Controlling hypersonic boundary layer transition with localized cooling and metasurface treatments.

This study investigates a novel method to control hypersonic boundary layer transition using a combined local cooling and local metasurface treatment. The method's effectiveness was investigated on a 5-degree half-angle blunt wedge with a nose radius of 0.0254 mm at a freestream Mach number of 6.0 using direct numerical simulations and linear stability theory. We explored four cases: (i) adiabatic baseline case, (ii) locally cooled case, (iii) local metasurface case, and (iv) combined local cooling-local metasurface case. Results showed that the combined local cooling-local metasurface treatment significantly reduced both wall pressure disturbance amplitude and the density perturbation amplitude around the sonic line, indicating a potential for controlling hypersonic boundary layer transition. In the local cooling-local metasurface case, the disturbance amplitude at the end of the computational domain was 270 times lower than the baseline case. The study also examined the impact of Reynolds numbers, ranging from 25.59 million per meter to 32.80 million per meter. Unsteady simulations revealed that the Reynolds number had a negligible effect on the local cooling-local metasurface performance, indicating that the proposed method applies to a wide range of flight conditions.

Modeling advanced air mobility aircraft in data-driven reduced order realistic urban winds.

The concept of Advanced Air Mobility involves utilizing cutting-edge transportation platforms to transport passengers and cargo efficiently over short distances in urban and suburban areas. However, using simplified atmospheric models for aircraft simulations can prove insufficient for modeling large disturbances impacting low-altitude flight regimes. Due to the complexities of operating in urban environments, realistic wind modeling is necessary to ensure trajectory planning and control design can maintain high levels of safety. In this study, we simulate the dynamic response of a representative advanced air mobility platform operating in wing-borne flight through an urban wind field generated using Large Eddy Simulations (LES) and a wind field created using reduced-order models based on full-order computational solutions. Our findings show that the longitudinal response of the aircraft was not greatly affected by the fidelity of the LES models or if the spatial variation was considered while evaluating the full-order wind model. This is encouraging as it indicates that the full LES generation of the wind field may not be necessary, which decreases the complexity and time needed in this analysis. Differences are present when comparing the lateral response, owing to the differences in the asymmetric loading of the planform in the full and reduced order models. These differences seen in the lateral responses are expected to increase for planforms with smaller wing loadings, which could pose challenges. Additionally, the response of the aircraft to the mean wind field, the temporal average of the full order model, was misrepresentative in the longitudinal response and greatly under-predicted control surface activity, particularly in the lateral response.

An efficient quantum partial differential equation solver with chebyshev points.

Differential equations are the foundation of mathematical models representing the universe's physics. Hence, it is significant to solve partial and ordinary differential equations, such as Navier-Stokes, heat transfer, convection-diffusion, and wave equations, to model, calculate and simulate the underlying complex physical processes. However, it is challenging to solve coupled nonlinear high dimensional partial differential equations in classical computers because of the vast amount of required resources and time. Quantum computation is one of the most promising methods that enable simulations of more complex problems. One solver developed for quantum computers is the quantum partial differential equation (PDE) solver, which uses the quantum amplitude estimation algorithm (QAEA). This paper proposes an efficient implementation of the QAEA by utilizing Chebyshev points for numerical integration to design robust quantum PDE solvers. A generic ordinary differential equation, a heat equation, and a convection-diffusion equation are solved. The solutions are compared with the available data to demonstrate the effectiveness of the proposed approach. We show that the proposed implementation provides a two-order accuracy increase with a significant reduction in solution time.

Multifidelity computing for coupling full and reduced order models.

Hybrid physics-machine learning models are increasingly being used in simulations of transport processes. Many complex multiphysics systems relevant to scientific and engineering applications include multiple spatiotemporal scales and comprise a multifidelity problem sharing an interface between various formulations or heterogeneous computational entities. To this end, we present a robust hybrid analysis and modeling approach combining a physics-based full order model (FOM) and a data-driven reduced order model (ROM) to form the building blocks of an integrated approach among mixed fidelity descriptions toward predictive digital twin technologies. At the interface, we introduce a long short-term memory network to bridge these high and low-fidelity models in various forms of interfacial error correction or prolongation. The proposed interface learning approaches are tested as a new way to address ROM-FOM coupling problems solving nonlinear advection-diffusion flow situations with a bifidelity setup that captures the essence of a broad class of transport processes.

Interface learning of multiphysics and multiscale systems.

Complex natural or engineered systems comprise multiple characteristic scales, multiple spatiotemporal domains, and even multiple physical closure laws. To address such challenges, we introduce an interface learning paradigm and put forth a data-driven closure approach based on memory embedding to provide physically correct boundary conditions at the interface. To enable the interface learning for hyperbolic systems by considering the domain of influence and wave structures into account, we put forth the concept of upwind learning toward a physics-informed domain decomposition. The promise of the proposed approach is shown for a set of canonical illustrative problems. We highlight that high-performance computing environments can benefit from this methodology to reduce communication costs among processing units in emerging machine-learning-ready heterogeneous platforms toward exascale era.

Results of Posterior Vertebral Column Resection: Surgical Modification of Suk Technique.

STUDY DESIGN: Consecutive, retrospective review. OBJECTIVES: To evaluate and report a modified posterior vertebral column technique. METHODS: We present a retrospective analysis of 20 patients. Patients having severe 3-dimensional deformity with flexibility less than 20% and managed by posterior vertebral body resection (PVCR) between 2011 and 2014 were included in this study. There were 12 female and 8 male patients, with a mean age of 18 year (range = 3-63 years). RESULTS: The average follow-up was 3.5 years (2-5 years). The preoperative coronal plane deformity was 84° (70° to 120°) and corrected to 42° (28° to 68°), showing 60% scoliosis correction. Average preoperative local kyphotic angle was 92° (82° to 110°). Correction rate for kyphosis was 62%. All patients after surgery showed their baseline neurological status, and no complications were encountered. The mean estimated blood loss was 1072 mL (350-2000 mL). Thirty-nine percent (33% to 50%) of total blood loss occurred after vertebral body resection, and 61% (50% to 67%) blood loss occurred after the removal of posterior elements. The ratio of estimated blood loss to estimated body blood volume was 26% (range = 19% to 52%). CONCLUSION: We found that 60% of total bleeding occurs during and after posterior bone resection. Spinal cord is open to possible iatrogenic direct spinal cord injury with surgical instruments for a much shorter period of time compared with the original technique.

The Results of Hemivertebra Resection by the Posterior Approach in Children with a Mean Follow-Up of Five Years.

AIM: To evaluate the radiologic and clinical results of patients who underwent deformity correction and stabilization for congenital spinal deformities using pedicle screws after hemivertebra resection. MATERIAL AND METHOD: Nine patients, mean age 9.2, who underwent posterior hemivertebrectomy and transpedicular fixation for congenital spinal deformity and had longer than five years of follow-up were evaluated retrospectively. The hemivertebrae were located in the thoracic region in 4 patients and thoracolumbar transition region in 5 patients. The patients were evaluated radiologically and clinically in the postoperative period. RESULTS: Mean length of follow-up was 64.2 months. The mean operating time was 292 minutes. The mean blood loss was 236 mL. The average hospitalization time was 7 days. The amount of correction on the coronal planes was measured as 31%. The mean segmental kyphosis angle was 45.7 degrees preoperatively and it was measured 2.7 degrees in the follow-up period. There were no statistically significant differences between the early postoperative period and final follow-up X-rays with respect to coronal and sagittal plane deformities. CONCLUSION: The ability to obtain a sufficient and balanced correction in the cases accompanied by long compensator curvatures that have a structural character in hemivertebra may require longer fusion levels.

Posttraumatic Charcot (Neuropathic) Spinal Arthropathy at the Cervicothoracic Junction.

BACKGROUND: Charcot spine arthropathy (posttraumatic neuroarthropathy of the spine) has been reported to be a very late and rare complication of spinal cord injury. Charcot of the cervicothoracic and upper thoracic region rarely is reported in the literature. Charcot spinal arthropathy is a cause of progressive deformity and may present as late as 30 years after the original spinal cord injury. This is more common in paraplegic patients who are actively ambulating. CASE DESCRIPTION: A 56-year-old patient with complete paraplegia for approximately 20 years after spinal cord injury presented with severe kyphous deformity and instability of thoracolumbar spine. His sensory level to deep pain was at thoracic (D4). He kept developing new neuroarthropathies at different segments within a span of 5-6 months after every decompression and fusion with anterior cage and posterior instrumentation done. A total of 3 surgeries had been done in span of 2 years, initially thoracic, then lumbar and finally cervicothoracic junction. CONCLUSIONS: We present this case because of the challenges in surgery for instrumentation of new Charcot spinal arthropathy. Reports of neuroarthropathy developing above the level of spinal cord injury and at the cervicothoracic junction are rare. The treating surgeon should be cognizant of the possibility of developing secondary levels of neuroarthropathy above and below a previously successful fusion.

Traumatic lumbosacral spondyloptosis: a case report and review of the literature.

Study Design Case report and review of the literature. Objective To report a case of traumatic L5-S1 spondyloptosis and review the literature. Method A 28-year-old man presented with severe low back pain, numbness at the soles of feet, and bowel and bladder dysfunction. Two days before admission, a tree trunk fell on his back while he was seated. A two-stage posterior-anterior procedure was performed. At the first stage, posterior decompression, reduction, and fusion with instrumentation were performed. At the second stage, which was performed 6 days after the first stage, the patient underwent anterior lumbar interbody fusion. The patient received physical therapy 1 week after the second stage. Results The patient's numbness improved immediately after the first posterior surgery. His fecal and urinary incontinence improved 6 months after discharge. He has been pain-free for a year and has returned to work. Conclusion A PubMed search was performed using the following keywords: lumbosacral spondyloptosis, lumbosacral dislocation, and L5-S1 traumatic dislocation. The search returned only nine reported cases of traumatic spondyloptosis. Traumatic spondyloptosis at the lumbosacral junction is a rare ailment that should be suspected in cases of high, direct, and posterior impact on the low lumbar area, and surgical treatment should be the standard choice of care.