Modeling of the Flow Rate in the Dispensing-Based Process for Fabricating Tissue Scaffolds

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
X. B. Chen ◽  
M. G. Li ◽  
H. Ke
Keyword(s):  
Flow Rate ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Chitosan Solution ◽  
Tissue Scaffolds ◽  
Fabrication Process ◽  
3D Scaffold ◽  
Needle Size ◽  
Scaffold Fabrication

Made from biomaterials, tissue scaffolds are three-dimensional (3D) constructs with highly interconnected pore networks for facilitating cell growth and flow transport of nutrients and metabolic waste. To fabricate the scaffolds with complex structures, dispensing-based rapid prototyping technique has been employed recently. In such a fabrication process, the flow rate of biomaterial dispensed is of importance since it directly contributes to the pore size and porosity of the scaffold fabricated. However, the modeling of the flow rate has proven to be a challenging task due to its complexity. This paper presents the development of a model for the flow rate in the scaffold fabrication process based on the fundamentals of fluid mechanics. To verify the effectiveness of the developed model, experiments were carried out, in which the chitosan solution (2% w/v) in acetic acid was used for dispensing under different applied pressures (50kPa, 100kPa, 150kPa, 200kPa, and 250kPa) and needle heater temperatures (25°C, 35°C, 50°C, and 65°C). The measured flow rates were used to identify the flow behavior of the solution and were compared to the predictions from the developed model to illustrate the model effectiveness. Based on the developed model, simulations were carried out to identify the effects of the needle size and the flow behavior on the flow rate in the scaffold fabrication process. The developed model was also applied to determine the dispensing conditions for fabricating 3D scaffolds from a 50% chitosan-hydroxyapatite colloidal gel. As an example, a scaffold fabricated with a well-controlled internal structure of diameters of 610±43μm and pore sizes of 850±75μm in the horizontal plane and of 430±50μm in the vertical direction is presented in this paper to illustrate the promise of the developed model as applied to the 3D scaffold fabrication.

Modeling the Flow Behavior and Flow Rate of Medium Viscosity Alginate for Scaffold Fabrication With a Three-Dimensional Bioplotter

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Md. Sarker ◽  
X. B. Chen
Keyword(s):  
Flow Rate ◽  
Flow Behavior ◽  
Slip Flow ◽  
Three Dimensional ◽  
Layer By Layer ◽  
Rate Model ◽  
Scaffold Fabrication ◽  
Model Equations ◽  
Printing Techniques ◽  
Medium Viscosity

Tissue regeneration with scaffolds has proven promising for the repair of damaged tissues or organs. Dispensing-based printing techniques for scaffold fabrication have drawn considerable attention due to their ability to create complex structures layer-by-layer. When employing such printing techniques, the flow rate of the biomaterial dispensed from the needle tip is critical for creating the intended scaffold structure. The flow rate can be affected by a number of variables including the material flow behavior, temperature, needle geometry, and dispensing pressure. As such, model equations can play a vital role in the prediction and control of the flow rate of the material dispensed, thus facilitating optimal scaffold fabrication. This paper presents the development of a model to represent the flow rate of medium viscosity alginate dispensed for the purpose of scaffold fabrication, by taking into account the shear and slip flow from a tapered needle. Because the fluid flow behavior affects the flow rate, model equations were also developed from regression of experimental data to represent the flow behavior of alginate. The predictions from both the flow behavior equation and flow rate model show close agreement with experimental results. For varying needle diameters and temperatures, the slip effect occurring at the needle wall has a significant effect on the flow rate of alginate during scaffold fabrication.

Effect of Outer Fin Axial Gap on the Sealing Effectiveness and Fluid Dynamics of Radial Rim Seal

2017 ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Liming Song ◽  
Qing Gao ◽  
Xin Yan ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Flow Rate ◽  
Gas Turbines ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Navier Stokes ◽  
Hot Gas

The modern gas turbine is widely applied in the aviation propulsion and power generation. The rim seal is usually designed at the periphery of the wheel-space and prevented the hot gas ingestion in modern gas turbines. The high sealing effectiveness of rim seal can improve the aerodynamic performance of gas turbines and avoid of the disc overheating. Effect of outer fin axial gap of radial rim seal on the sealing effectiveness and fluid dynamics was numerically investigated in this work. The sealing effectiveness and fluid dynamics of radial rim seal with three different outer fin axial gaps was conducted at different coolant flow rates using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and SST turbulent model solutions. The accuracy of the presented numerical approach for the prediction of the sealing performance of the turbine rim seal was demonstrated. The obtained results show that the sealing effectiveness of radial rim seal increases with increase of coolant flow rate at the fixed axial outer fin gap. The sealing effectiveness increases with decrease of the axial outer fin gap at the fixed coolant flow rate. Furthermore, at the fixed coolant flow rate, the hot gas ingestion increases with the increase of the axial outer fin gap. This flow behavior intensifies the interaction between the hot gas and coolant flow at the clearance of radial rim seal. The preswirl coefficient in the wheel-space cavity is also illustrated to analyze the flow dynamics of radial rim seal at different axial outer fin gaps.

Unsteady Responses of the Impeller of a Centrifugal Compressor Exposed to Pulsating Backpressure

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Mengying Shu ◽  
Mingyang Yang ◽  
Ricardo F. Martinez-Botas ◽  
Kangyao Deng ◽  
Lei Shi
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Combustion Engine ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Intake Manifold ◽  
Unsteady Simulation

The flow in intake manifold of a heavily downsized internal combustion engine has increased levels of unsteadiness due to the reduction of cylinder number and manifold arrangement. The turbocharger compressor is thus exposed to significant pulsating backpressure. This paper studies the response of a centrifugal compressor to this unsteadiness using an experimentally validated numerical method. A computational fluid dynamic (CFD) model with the volute and impeller is established and validated by experimental measurements. Following this, an unsteady three-dimensional (3D) simulation is conducted on a single passage imposed by the pulsating backpressure conditions, which are obtained by one-dimensional (1D) unsteady simulation. The performance of the rotor passage deviates from the steady performance and a hysteresis loop, which encapsulates the steady condition, is formed. Moreover, the unsteadiness of the impeller performance is enhanced as the mass flow rate reduces. The pulsating performance and flow structures near stall are more favorable than those seen at constant backpressure. The flow behavior at points with the same instantaneous mass flow rate is substantially different at different time locations on the pulse. The flow in the impeller is determined by not only the instantaneous boundary condition but also by the evolution history of flow field. This study provides insights in the influence of pulsating backpressure on compressor performance in actual engine situations, from which better turbo-engine matching might be benefited.

Bio-Rapid-Prototyping of Tissue Engineering Scaffolds and the Process-Induced Cell Damage

2013 ◽  
Vol 17 ◽  
pp. 1-23 ◽  
Author(s):  
Xiao Yu Tian ◽  
Ming Gan Li ◽  
Xiong Biao Chen
Keyword(s):  
Tissue Engineering ◽  
Rapid Prototyping ◽  
Cell Damage ◽  
Cell Encapsulation ◽  
Tissue Scaffolds ◽  
Fabrication Process ◽  
Laser Exposure ◽  
Ongoing Research ◽  
Research Attention ◽  
Scaffold Fabrication

Tissue scaffolds play a vital role in tissue engineering by providing a native tissue-mimicking environment for cell proliferation and differentiation as well as tissue regeneration. Fabrication of tissue scaffolds has been drawing increasing research attention and a number of fabrication techniques have been developed. To better mimic the microenvironment of native tissues, novel techniques have emerged in recent years to encapsulate cells into the engineered scaffolds during the scaffold fabrication process. Among them, bio-Rapid-Prototyping (bioRP) techniques, by which scaffolds with encapsulated cells can be fabricated with controlled internal microstructure and external shape, shows significant promise. It is noted in the bioRP processes, cells may be continuously subjected to environmental stresses such as mechanical, electrical forces and laser exposure. If the stress is greater than a certain level, the cell membrane may be ruptured, leading to the so-called process-induced cell damage. This paper reviews various cell encapsulation techniques for tissue scaffold fabrication, with emphasis on the bioRP technologies and their technical features. To understand the process-induced cell damage in the bioRP processes, this paper also surveys the cell damage mechanisms under different stresses. The process-induced cell damage models are also examined to provide a cue to the cell viability preservation in the fabrication process. Discussions on further improvements of bioRP technologies are given and ongoing research into mechanical cell damage mechanism are also suggested in this review.

High-Temperature and High-Pressure Steam Flow Through a Steam Turbine Bypass Valve Line

2005 ◽  
Author(s):  
R. S. Amano
Keyword(s):  
High Pressure ◽  
Flow Rate ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Steam Flow ◽  
Navier Stokes ◽  
Data Set ◽  
Bypass Valve ◽  
Valve Opening ◽  
Energy Equations

The objective of the present study is to investigate the steam flow behavior through the high-pressure turbine bypass valve. Efforts have mainly been directed at investigating the process of steam flow and property variations aforementioned bypass valve as well as to obtain correlations between the flow rate and the valve opening ratio. Modeling of the high-pressure turbulent steam flow was performed on a three-dimensional non-staggered (co-located) grid system by employing the finite volume method and by solving the three-dimensional, turbulent, compressible Navier-Stokes, and energy equations. Through this research, numerous data have been acquired and analyzed. These efforts enable us to obtain a correlation data set for the flow rate coefficient as a function of valve opening. One of the significant accomplishments is to use the model presented here for further improve a design of a turbine bypass flow valve.

Metal Flow Behavior on the Non-Uniform Wall Thickness Three-Way Valve Extrusion

2008 ◽  
Vol 575-578 ◽  
pp. 328-333 ◽  
Author(s):  
Mei Cheng ◽  
Zhi Min Zhang
Keyword(s):  
Flow Behavior ◽  
Metal Flow ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Extrusion Process ◽  
Shell Shape ◽  
Uniform Temperature ◽  
Uniform Wall ◽  
Simulation Results ◽  
Loading Sequence

High pressure valve always takes several dozens to several hundreds MPa pressure and which was difficulty to form because of its complex internal structure. In this paper, three-dimensional numerical simulation was carried out to investigate metal flow behavior during the three-way valve extrusion process. The block shape materials were formed to shell shape three-way components by the level and vertical direction uniform temperature simultaneous extrusion. The simulation results show that the metal flows were influenced by both loading sequence and time of the moving die of two directions. The loading process worked out through dynamic simulation can guide the actual processing.

Modeling of Flow Rate, Pore Size, and Porosity for the Dispensing-Based Tissue Scaffolds Fabrication

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
M. G. Li ◽  
X. Y. Tian ◽  
X. B. Chen
Keyword(s):  
Mechanical Properties ◽  
Pore Size ◽  
Compressive Stress ◽  
Flow Rate ◽  
Tissue Scaffolds ◽  
Fabrication Process ◽  
Scaffold Material ◽  
Pore Sizes ◽  
Moving Speed

Dispensing technique is one of the promising solid freeform (SFF) methods to fabricate scaffolds with controllable pore sizes and porosities. In this paper, a model to represent the dispensing-based SFF fabrication process is developed. Specifically, the mechanical properties of the scaffold material and its influence on the fabrication process are examined; the flow rate of the scaffold material dispensed and the pore size and porosity of the scaffold fabricated in the process are represented. In order to generate scaffold strands without either tensile or compressive stress, the optimal moving speed of the dispensing head is determined from the flow rate of the scaffold material dispensed. Experiments were also carried out to illustrate the effectiveness of the model developed.

Water Spray Cooling of High-Temperature Steam Flow Through a Steam Turbine Bypass Valve Line

2009 ◽  
Author(s):  
R. S. Amano
Keyword(s):  
High Pressure ◽  
Flow Rate ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Steam Flow ◽  
Navier Stokes ◽  
Data Set ◽  
Bypass Valve ◽  
Valve Opening ◽  
Energy Equations

The objective of the present study is to investigate the steam flow behavior through the high-pressure turbine bypass valve. Efforts have mainly been directed at investigating the process of steam flow and property variations aforementioned bypass valve as well as to obtain correlations between the flow rate and the valve opening ratio. Modeling of the high-pressure turbulent steam flow was performed on a three-dimensional non-staggered (co-located) grid system by employing the finite volume method and by solving the three-dimensional, turbulent, compressible Navier-Stokes, and energy equations. Through this research, numerous data have been acquired and analyzed. These efforts enable us to obtain a correlation data set for the flow rate coefficient as a function of valve opening. One of the significant accomplishments is to use the model presented here for further improve a design of a turbine bypass flow valve.

scholarly journals Aligned 3D porous polyurethane scaffolds for biological anisotropic tissue regeneration

2019 ◽  
Author(s):  
Weiwei Lin ◽  
Wanling Lan ◽  
Yingke Wu ◽  
Daiguo Zhao ◽  
Yanchao Wang ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Tissue Regeneration ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Waterborne Polyurethane ◽  
3D Scaffold ◽  
Pure Material ◽  
Muscle Nerve

Abstract A green fabrication process (organic solvent-free) of artificial scaffolds is required in tissue engineering field. In this work, a series of aligned three-dimensional (3D) scaffolds are made from biodegradable waterborne polyurethane (PU) emulsion via directional freeze–drying method to ensure no organic byproducts. After optimizing the concentration of polymer in the emulsion and investigating different freezing temperatures, an aligned PUs scaffold (PU14) generated from 14 wt% polymer content and processed at −196°C was selected based on the desired oriented porous structure (pore size of 32.5 ± 9.3 μm, porosity of 92%) and balanced mechanical properties both in the horizontal direction (strength of 41.3 kPa, modulus of 72.3 kPa) and in the vertical direction (strength of 45.5 kPa, modulus of 139.3 kPa). The response of L929 cells and the regeneration of muscle tissue demonstrated that such pure material-based aligned 3D scaffold can facilitate the development of orientated cells and anisotropic tissue regeneration both in vitro and in vivo. Thus, these pure material-based scaffolds with ordered architecture have great potentials in tissue engineering for biological anisotropic tissue regeneration, such as muscle, nerve, spinal cord and so on.

Sign in / Sign up

Export Citation Format

Share Document