3D Optical Scanning Research Articles

A device-agnostic shape model for automated body composition estimates from 3D optical scans.

Many predictors of morbidity caused by metabolic disease are associated with body shape. 3D optical (3DO) scanning captures body shape and has been shown to accurately and precisely predict body composition variables associated with mortality risk. 3DO is safer, less expensive, and more accessible than criterion body composition assessment methods such as dual-energy X-ray absorptiometry (DXA). However, 3DO scanning has not been standardized across manufacturers for pose, mesh resolution, and post processing methods. We introduce a scanner-agnostic algorithm that automatically fits a topologically consistent human mesh to 3DO scanned point clouds and predicts clinically important body metrics using a standardized body shape model. Our models transform raw scans captured by any 3DO scanner into fixed topology meshes with anatomical consistency, standardizing the outputs of 3DO scans across manufacturers and allowing for the use of common prediction models across scanning devices. A fixed-topology body mesh template was automatically registered to 848 training scans from three different 3DO systems. Participants were between 18 and 89 years old with body mass index ranging from 14 to 52kg/m2 . Scans were registered by first performing a coarse nearest neighbor alignment between the template and the input scan with an anatomically constrained principal component analysis (PCA) domain deformation using a device and gender specific bootstrap basis trained on 70 seed scans each. The template mesh was then optimized to fit the target with a smooth per-vertex surface-to-surface deformation. A combined unified PCA model was created from the superset of all automatically fit training scans including all three devices. Body composition predictions to DXA measurements were learned from the training mesh PCA coefficients using linear regression. Using this final unified model, we tested the accuracy of our body composition models on a withheld sample of 562 scans by fitting a PCA parameterized template mesh to each raw scan and predicting the expected body composition metrics from the principal components using the learned regression model. We achieved coefficients of determination (R2 ) above 0.8 on all nine fat and lean predictions except female visceral fat (0.77). R2 was as high as 0.94 (total fat and lean, trunk fat), and all root-mean-squared errors were below 3.0kg. All predicted body composition variables were not significantly different from reference DXA measurements except for visceral fat and female trunk fat. Repeatability precision as measured by the coefficient of variation (%CV) was around 2-3x worse than DXA precision, with visceral fat %CV below 2x DXA %CV and female total fat mass at 5x. Our method provides an accurate, automated, and scanner agnostic framework for standardizing 3DO scans and a low cost, radiation-free alternative to criterion radiology imaging for body composition analysis. We published a web-app version of this work at https://shapeup.shepherdresearchlab.org/3do-bodycomp-analyzer/ that accepts mesh file uploads and returns templated meshes with body composition predictions for demo purposes.

Position-Sensitive Bulk and Surface Element Analysis of Decorated Porcelain Artifacts.

Non-destructive characterization of decorated porcelain artifacts requires the joint use of surface-analytical methods for the decorative surface pattern and methods of high penetration depth for bulk-representative chemical composition. In this research, we used position-sensitive X-ray Fluorescence Spectrometry (XRF) and Prompt-gamma activation analysis (PGAA) for these purposes, assisted by 3D structured-light optical scanning and dual-energy X-ray radiography. The proper combination of the near-surface and bulk element composition data can shed light on raw material use and manufacturing technology of ceramics.

Visualization and quantitative statistics of experimental hydraulic fracture network based on optical scanning

The formation of hydraulic fracture-network is an important goal for stable and increased production of unconventional oil and gas resources. However, due to the extremely complex mechanical behavior of hydraulic-fracture propagation, there is still a lack of fine, effective and systematic evaluation methods on 3D fracture-network structure. The quantitative characterization of hydraulic-fractures is of great significance to reveal the law of fracture propagation and to evaluate the reservoir stimulation effectiveness reasonably. Although the micro-cracks evolution process follows a random rather than deterministic pattern, the overall fracture morphology is featuring statistical regularity. In this study, after the indoor hydraulic-fracturing simulation experiments of the tight sandstone specimens, 3D optical scanning was used to visualize the fracture-network. On this basis, two aspects of quantitative statistics of 3D complex fracture-networks were established by plane and sphere cuttings for the first time, including angle distribution statistics and spatial variation statistics. Comparative analyses with reported methods showed that, the overall deflection of the macroscopic fracture-networks varies synchronously with the local roughness of the main hydraulic fractures closest to the wellbore, which satisfied exponential function or power-law function relationship between them. The variation of the area proportion with the propagation radius reflects the specific fracture propagation process such as crack initiation, bifurcation and arrest, and could be used to assess the complexity of the fracture-network. Moreover, a new stimulation evaluation index Es was established by comprehensively considering the stimulated-reservoir-area, the dispersion degree of the angle distribution and the complexity of spatial variation for 3D fracture-network. The insights gained warrant further applicability on hydraulic-fracturing in the actual engineering scale.

Scanning accuracy with splinted and unsplinted implant scan bodies for the edentulous arch atimplant level: an in vitro study.

Accuracy of completely edentulous arch scanning with implant scan bodies has not been completely validated for intraoral scanners. For desktop laboratory scanners validations were found in the literature. The aim of this in vitro study was to compare the dimensional accuracy of scanning with splinted and unsplinted scan bodies on a completely edentulous maxillary arch with 6 implants. A maxillary edentulous master cast with 6 implants was used as control for all implant level impressions. 6 implants were digitally planned and placed at different angulation of 0, 0 17° and 30°. A contact coordinate measuring machine (CMM) was used to generate baseline linear measurements of the master cast. Four test groups included: 2 intraoral scanners Trios (3shape, Copenhagen, Denmark) and True Definition (3M ESPE, St Paul, MN), one industrial scanner Atos (Core optical 3D scanner) and one conventional impression group scanned with laboratory scanner Dental Wings 7 Series. Each scan recording was made with splinted and unsplinted scan bodies. Digital datasets of all measurements were compared with the CMM baseline values using PolyWorks® InnovMetric Software in order to assess the linear and angular deviations and determine the accuracy of complete arch digital impression. Factorial ANOVA showed significant effect with splinting, scanner type, inter-implant distance and implant angulation for linear deviations. Splinted scan bodies revealed elevated linear and angular deviation values for all scanners with significantly highest deviations for True Definition scanner. Significant correlation was found between inter-implant distance and linear deviation (r =0.45, P =<0.001) with increased linear deviations among all scanners, regardless of splinting. ( P <0.05). Significant effect on accuracy was seen for angular deviation with splinting, scanner type and implant angulation; significant difference was found between 0° and 30° implant angulation ( P =0.035) with more deviation with 30° implant angulation. The accuracy of the complete arch implant digital impression using splinted scan bodies was significantly reduced for measurements that crossed the arch midline. The digital impression technique using a broad splint design to connect scan bodies was not found to improve the scan accuracy for intraoral scanners.

In vitro method to quantify and visualize mechanical wear in human meniscus subjected to joint loading

The mechanical wear and tear of soft connective tissue from repetitive joint loading is a primary factor in degenerative joint disease, and therefore methods are needed to accurately characterize wear in joint structures. Here, we evaluate the accuracy of using a structured light 3D optical scanning system and modeling software to quantify and visualize volume loss in whole human meniscus subjected to in vitro joint loading. Using 3D printed meniscus replicas with known wear volumes, we determined that this novel imaging method has a mean accuracy of approximately 13 mm3, corresponding to a mean error of less than 7% when measuring meniscal volumetric changes of 0.2 cm3 (size of a pea). The imaging method was then applied to measure the in vitro wear of whole human menisci at four time points when a single cadaveric knee was subjected to one million cycles of controlled joint loading. The medial and lateral menisci reached steady state volumetric reductions of 0.72 cm3 and 0.34 cm3 per million cycles, respectively. Colorimetric maps of linear wear depth revealed high wear and deformation in the posterior regions of both the medial and lateral menisci. For the first time, this study has developed a method to accurately characterize volume loss in whole meniscus subjected to in vitro joint loading. This 3D scanning method offers researchers a new investigative tool to study mechanical wear and joint degeneration in meniscus, and other soft connective tissues.

Older adults’ facial characteristics compared to young adults’ in correlation with edentulism: a cross sectional study

BackgroundFacial ageing is a result of superficial wrinkling combined with changes to the underlying soft tissues and skeleton. The influence of tooth loss, as a geriatric characteristic, on facial appearance is still poorly explained. The aim was to evaluate the facial characteristics of older adults, correlate these characteristics with the dentition and make comparisons with young adults using a non-invasive 3D methodology.Methods90 participants older than 65 years, classified into 3 subgroups (edentulous, partially edentulous, toothed) and 30 young adults were evaluated. Their faces were scanned with an optical Artec 3D-scanner. Cephalometric analyses were made using the RapidForm computer program. An independent t-test and ANOVA were used for the comparisons. Pairwise, post-hoc tests were applied with respect to the significant differences (P < 0.05).ResultsThe faces of older adults are wider and longer because of the longer middle facial height. Older adults also have a longer upper lip, a larger nose, a smaller nasolabial angle (due to the nasal ptosis), narrower upper- and lower-lip vermilions and larger facial and lower-facial-height angles, resulting in a flat facial profile.The facial changes due to ageing are the most pronounced in the edentulous. In comparison with the toothed, they have a smaller facial height due to the smaller lower facial height, larger nasolabial angle, smaller mouth width, shorter upper lip and narrower lip vermilions. Their profile is flatter and their lips are more retruded.ConclusionsThe proportions of the whole face are changed in older adults and they are the most expressed when this is combined with tooth loss.

Experimentally validated modeling of the temperature distribution and the distortion during the Fused Filament Fabrication process

This paper presents the numerical approach to compute process-induced temperature distribution and distortion in Polylactic Acid (PLA) parts manufactured using the Fused Filament Fabrication (FFF) process. Thermal simulations are performed first to compute the time-dependent temperature distribution which is then input as solution-independent boundary condition into a mechanical simulation to compute warpage of the manufactured part. The developed procedure used experimentally measured process parameters and was experimentally verified at each step of the simulation. The thermal step in the simulation workflow was experimentally validated using thermography yielding quantitative predictions for 25 out of 27 considered points with the highest accuracy of <1°C. To verify mechanical step, the computed process-induced distortions were compared against those measured with an optical 3D scanner. The developed procedure yielded qualitative and, in some cases, quantitative predictions of process-induced geometrical distortions.

Impact of the Internal Structure Density in the Process of Fabrication of Orthodontic Master Models by Fused Deposition Modeling

Abstract The article focuses on the influence of infill (internal structure of components) in the dimensional accuracy of dental master models during the processes of their fabrication by Fused Deposition Modeling (FDM) technology, and their vacuuming process for production of clear orthodontic aligners. The components, in this case, were the upper jaws (maxillary teeth) of two individual patients (Tzina, Dimitris), which were obtained by intraoral 3D scanning. Patient Tzina at the time of intra-oral scanning was 27 years old and Dimitris was 23 years old. The method of 3D printing was the FDM, and the material used in this research was thermoplastic high impact polystyrene (HIPS). Three different percentages of infill density were set, 60%, 80%, and 100%. For each setting, there were five specimens (thirty 3D printed dental models in total, 15 for Tzina and 15 for Dimitris). After the 3D printing, the models were digitized and measured by GOM ATOS II Triple Scan MV 170 optical 3D scanner and compared with the values of the initial digital models. Then the dental master models underwent the process of Essix-aligners formation (single press) and were rescanned and measured again. The outcome of this research was to examine if the dental master models remain dimensionally accurate after these processes, and which infill provides the optimal and medically approved accuracy.

An evaluation of three-dimensional facial changes after surgically assisted rapid maxillary expansion (SARME): an observational study

BackgroundThe abnormal facial features in maxillary transverse deficiency (MTD) are minimal and limited to a deficiency of the middle facial third, narrow nares and nasal base, and deepened nasolabial folds. The surgical expansion of the narrow maxilla has most obvious effects on widening of the maxillary dental arch and expansion of the maxillary and palatal structures in the transverse plane, however sagittal changes also occurs. The purpose of this observational study was to evaluate the three-dimensional (3D) facial soft tissue changes following surgically assisted rapid maxillary expansion (SARME).MethodsIn 15 skeletally mature patients with severe maxillary transverse deficiency, the planned maxillary expansion (on average 8.8 mm ± 2.3 mm) was achieved with a bone-borne palatal distractor. The 3D optical scans of the facial surface were obtained before and six months after SARME. In the first part, we defined different anatomical landmarks on both scans and compared cephalometric measurements. In the second part, we registered both 3D scans in the same workplace using the regional best-fit method (forehead, supraorbital and nasal root regions were selected for the superimposition) and conducted surface analysis.ResultsThe largest differences between the pre- and post-operation scans were observed in the paranasal and cheek area (1.4 ± 1.0 mm). Significant differences occurred for an increased nasal width, a decreased upper-face height with an unchanged lower height, an increased vertical philtrum height and an increased nasolabial angle. A significant increase in the facial profile angle was also observed, resulting in an increased facial convexity and anterior displacement of the upper-lip area.ConclusionsThe widening of the nose and increased projection in the cheek and paranasal area in the lateral direction after maxillary expansion were confirmed; moreover, facial convexity increases, reflecting the underlying advancement of the maxilla.

Scoliosis Brace Finite Element Model and Preliminary Experimental Testing Using Electronic Speckle Pattern Interferometry

This article presents the results of numerical finite element method (FEM) simulations in the Ansys environment of a Boston orthopaedic brace. The geometric model was developed based on the results of digitisation performed by means of a three-dimensional (3D) optical scanner. A test stand for measurement of the brace’s field of displacements, utilising a laser electronic speckle pattern interferometer (ESPI), was used to experimentally verify the FEM model. During experimental testing, special attention was given to applying the loads and boundary conditions used in the numerical simulations. As a result, the relative difference between the experimentally and numerically determined displacements in the central part of orthoses amounted to approximately 0.6%. The experimentally verified FEM model was used to determine the force flow lines characteristic of the brace, indicating the general working method of the brace’s structure. The primary parts of the orthoses, carrying loads correcting the spine and the position of sites exerting little effort from the perspective of their participation in the orthoses’ essential therapeutic application were identified. The results obtained allow for the proposal of methods for mechanical optimisation of the brace’s design. The analysis conducted is universal in nature and can be adapted to other types of orthopaedic braces.

Study on the Stimulation Effectiveness Evaluation of Large-Scale Hydraulic Fracturing Simulation Experiment Based on Optical Scanning Technology

Summary Unconventional reservoirs such as gas shales and tight gas sands require technology-based solutions for optimum development because of the undeveloped matrix pores and poor permeability. Hydraulic fracturing is one of the most critical technologies. The quantitative characterization of hydraulic fractures is of great significance to the stimulation evaluation of the reservoir, but there is still a lack of fine, effective and systematic evaluation methods. 3D optical scanning technology is widely used in the quantitative characterization of rock fracture morphology for its advantages of high speed, convenience, high precision, and nondestructive testing. In this study, after the indoor hydraulic-fracturing simulation experiments, 3D optical scanning was used to visualize the fracture network. On this basis, two aspects of quantitative evaluation methods for stimulation effectiveness were established, including: (1) evaluating the local conductivity (permeability) of different fractures by cutting hydraulic-fracturing samples. Then combining local conductivity of different fractures with the overall stimulated reservoir area, which could be more reasonable to evaluate the stimulation scope of the reservoir; (2) calculating the fractal dimension (FD) of the 3D spatial structure based on the point-cloud processing, which could directly reflect the complexity of the fracture network. Finally, a new evaluation index for stimulation (Es) was established to comprehensively assess the stimulation effectiveness of the reservoir, which was applied and verified through the indoor fracturing simulation experiments of tight sandstone from the Ordos Basin, China.

An innovative location-dependent stochastic model for prediction steel bars area under chloride ion attack in the presence of transverse rebars

A novel location-dependent stochastic model is introduced for predicting the area of the corroded steel bars in the presence of transverse reinforcement. A 3D optical scanning technique was used to investigate the morphology and corrosion distribution patterns of different longitudinal steel rebars under various accelerated corrosion conditions. The result indicated that the existence of transverse bars significantly affects the corrosion pattern, which was not considered previously. Furthermore, it is shown that the Dagum probability function fits better to the scatter of areas. Utilizing zone-based lognormal function, a location-dependent stochastic model was developed to estimate the probable reduced rebars cross-section.

Emergence of the obesity epidemic: 6-decade visualization with humanoid avatars

Visualizations of the emerging obesity epidemic, such as with serial US color prevalence maps, provide graphic images that extend informative public health messages beyond those in written communications. Advances in low-cost 3D optical technology now allow for development of large image databases that include participants varying in race/ethnicity, body mass, height, age, and circumferences. When combined with contemporary statistical methods, these data sets can be used to create humanoid avatar images with prespecified anthropometric features. The current study aimed to develop a humanoid avatar series with characteristics of representative US adults extending over the past 6 decades. 3D optical scans were conducted on a demographically diverse sample of 570 healthy adults. Image data were converted to principal components and manifold regression equations were then developed with body mass, height, age, and waist circumference as covariates. Humanoid avatars were generated for representative adults with these 4 characteristics as reported in CDC surveys beginning in 1960-1962 up to 2015-2018. There was a curvilinear increase in adult US population body mass, waist circumference, and BMI in males and females across the 9 surveys spanning 6 decades. A small increase in average adult population age was present between 1960 and 2018; height changes were inconsistent. A series of 4 avatars developed at ∼20-y intervals for representative males and females reveal the changes in body size and shape consistent with the emergence of the obesity epidemic. An additional series of developed avatars portray the shapes and sizes of males and females at key BMI cutoffs. New mathematical approaches and accessible 3D optical technology combined with increasingly available large and diverse data sets across the life span now make unique visualization of body size and shape possible on a previously unattainable scale. This study is registered at https://clinicaltrials.gov/ct2/show/NCT03637855 as NCT03637855.

Shearing Performance of Natural Joints with Different Roughnesses under Direct Shearing Tests

Roughness is one of the major characteristics of natural fracture in hydrocarbon and geothermal reservoirs, which has a significant influence on the activation of fractures during hydraulic stimulation. The main purpose of this study is to investigate the effect of different roughnesses and high normal stresses on shear behaviors of rock joints. To do this, replicas of natural rock joint surfaces were constructed using the 3D optical scanning and 3D rigid engraving technique. Direct shear tests were performed on rock joint replicas with three joint roughness coefficient (JRC) indices (i.e., 1.42, 4.98, and 7.96) at two high normal load conditions (i.e., 15 and 30 MPa). The results show that the shear strength dependence on surface roughness is similar at normal stresses of 15 and 30 MPa. In addition, JRC-JCS shear strength criterion can reasonably describe the peak shear strengths that obtained from experimental curves, and the peak shear stresses have a positive correlation with JRC values at both normal stresses. Moreover, at normal stresses of 15 and 30 MPa, the shearing mechanism of joints with different JRC values is asperity shearing off. Results also show that the friction coefficient of joint surface increases as joint roughness increases, and higher normal loads may lead to a decrease of apparent cohesion, which weakens the residual strength during the slip. The results of this study improve insight into the natural fracture activation behavior during hydraulic fracturing.

Hot-Wire Investigation of Turbulence Topology behind Blades at Different Shape Qualities

The scope of this paper is to perform a detailed experimental investigation of the shape error effect on the turbulence evolution behind NACA 64-618 airfoil. This airfoil is 3D-printed with predefined typical shape inaccuracies. A high-precision optical 3D scanner was used to assess the shape and surface quality of the manufactured models. The turbulent flow was studied using hot-wire anemometry. The developed force balance device was provided to measure the aerodynamic characteristics of the airfoil. Experimental studies were carried out for three angles of attack, +10∘, 0∘, −10∘, and different chord-based Reynolds numbers from 5.3×104 to 2.1×105. The obtained results show that the blunt trailing edge and rough surface decline the aerodynamic performance of the blades. In addition, the experimental results revealed a strong sensitivity of the Taylor microscale Reynolds number to the type of shape inaccuracy, especially at Re≈1.7×105. We also discuss the evolution of the Reynolds stress components, the degree of flow anisotropy, and the power spectrum distributions depending on the airfoil inaccuracies.

Novel robotic technology for the rapid intraoperative manufacture of patient-specific instrumentation allowing for improved glenoid component accuracy in shoulder arthroplasty: a cadaveric study.

Accurate prosthesis placement in arthroplasty is an important factor in the long-term success of these interventions. Many types of guidance technology have been described to date often suffering from high costs, complex theater integration, time inefficiency, and problems with day-to-day usability. We present a novel, intraoperative robotics platform, capable of rapid, real-time manufacture of low-cost patient-specific guides while overcoming many of the issues with existing approaches. A prototype robotics platform was assessed in a 24-specimen cadaveric trial during sequential simulated shoulder arthroplasty procedures. The platform consisted of a tableside robot with sterile drapes and sterile disposable components. The robot itself comprised a 3D optical scanner, a 3-axis sterile robotic drill, and a 2-axis receptacle into which the disposable consumables were inserted. The consumable was composed of a region of rapidly setting moldable material and a clip allowing it to be reversibly attached to the robot. Computed tomographic (CT) imaging was obtained for all cadaveric specimens, and a surgical plan was created focusing on glenoid component position-specifically, guidewire position to allow for accurate glenoid preparation before implant insertion. Intraoperatively, for every specimen, the relevant osseous anatomy was exposed and humeral and glenoid preparation undertaken in the usual manner. The sterile disposable was used to create a mold of the joint surface. Once set, the mold was inserted into the robot and an optical scan of the surface was undertaken followed by automatic surface registration with the CT data and surgical plan. An automatic guide hole was subsequently drilled into the molded blank, which was removed from the robot and placed back into the patient, with the melded surface ensuring exact replacement. The guidewire was then driven through the guide hole in accordance with the preoperative plan. The novel robotic platform achieved average angular accuracies of 1.9° (standard deviation [SD] 1.3) version and 1.2° (SD 0.7) inclination with positional accuracy of 1.1 mm (SD 0.7) compared to a preoperative plan. We have described a novel robotics platform that is able to reliably produce patient-specific intraoperative guides to allow for accurate guidewire placement. Guidance is provided using a portable intraoperative device. The results suggest achieved accuracy levels may be equivalent to those seen in other existing guidance technologies; however, eventual invivo trials and analysis is required. This technology has potential transferability to improve accuracy in other areas of arthroplasty.

Study of process parameters of the atomizer-based spray gun for the application of a temporary matte coating for 3D scanning purposes

The aim of this paper is to find the most suitable process parameters of the spray gun for the deposition of matte coating for 3D optical scanning purposes. The membrane atomizer-based spray gun is used as a coating device. A suspension of TiO2 and ethanol is used as a coating material. In this study, the formed spray is analyzed using Phase Doppler Anemometry and the results are compared to the deposited coatings. Applied coatings are further examined using a profilometer and 3D scanner to analyze their thickness and the effect they have on the 3D surface reconstruction. The results of this work show that two spray layers are sufficient to evenly apply a coating with good properties for 3D optical scanning purposes. The coating thickness is below 1 μm, reference area is entirely scanned, and the scanned point cloud has a standard deviation from the reference plane below 1.1 μm.

Theoretical and experimental research on the quality of thermoformed foils using 3D-printed plastic moulds

An innovative approach to additive manufacturing consists in the possibility of producing moulds that can be used for traditional manufacturing processes such as thermoforming. The quality and dimensional precision of the interior surfaces of the plastic foils obtained after thermoforming is closely related to the used mould. The influencing factors considered are the different thermal and mechanical properties offered by the wide range of available plastic materials for additive manufacturing (AM), the multitude of printing parameters, and the technological process by means of which the mould was obtained. For the production of plastic moulds, Fused Filament Fabrication (FFF) and Selective Laser Sintering (SLS) processes, as well as materials specific to each technology, are used. This paper identifies and explains issues concerning the surface quality of the thermoformed foil through a systemic analysis approach and by conducting laboratory experiments. Optical 3D scanning equipment and software are employed to determine the proper additive process and materials for thermoforming process. The best quality of the finished product was obtained in the case of a male mould made by the SLS technology and PS foil with a thickness of 0.7 mm.

Withstanding Capacity of Machine Guards: Evaluation and Validation by 3D Scanners

Ballistic penetration of machine guards is a topic of great significance for ensuring safety and avoiding projection of objects out of the working space of machines. Although standardized tests are performed according to EU Directive 2006/42/EC, they have some limitations because they are carried out using a given penetrator that perpendicularly impacts a given surface of about 500 × 500 mm. Nevertheless, the withstanding capacity of those guards depends on a lot of different design parameters and physical quantities that have not been fully investigated. This paper is focused on the study of the influence of the machine guard size on the withstanding capacity to ballistic penetration throughout theoretical models and experimental tests based on an innovative method involving the use of 3D optical scanners for inspection. The experimental analyses described in this work, compared to theoretical results, demonstrate that a maximum plastic deformation area can be defined, independently of the plate size, given the same material, thickness, and penetrator. This result allows to set proper new ranges for standardized tests, overcoming the limitation of using specific sample sizes.

Effect of Manufacturing Inaccuracies on the Wake Past Asymmetric Airfoil by PIV

The effect of manufacturing geometry deviations on the flow past a NACA 64(3)-618 asymmetric airfoil is studied. This airfoil is 3D printed according to the coordinates from a public database. An optical high-precision 3D scanner, GOM Atos, measures the difference from the idealized model. Based on this difference, another model is prepared with a physical output closer to the ideal model. The velocity in the near wake (0–0.4 chord) is measured by using the Particle Image Velocimetry (PIV) technique. This work compares the wakes past three airfoil realizations, which differ in their similarity to the original design (none of the realizations is identical to the original design). The chord-based Reynolds number ranges from 1.6×104 to 1.6×105. The ensemble average velocity is used for the determination of the wake width and for the rough estimation of the drag coefficient. The lift coefficient is measured directly by using force balance. We discuss the origin of turbulent kinetic energy in terms of anisotropy (at least in 2D) and the length-scales of fluctuations across the wake. The spatial power spectral density is shown. The autocorrelation function of the cross-stream velocity detects the regime of the von Karmán vortex street at lower velocities.