40,143 research outputs found
Analytical modelling in Dynamo
BIM is applied as modern database for civil
engineering. Its recent development allows to preserve
both structure geometrical and analytical information. The
analytical model described in the paper is derived directly
from BIM model of a structure automatically but in most
cases it requires manual improvements before being sent
to FEM software. Dynamo visual programming language
was used to handle the analytical data. Authors developed
a program which corrects faulty analytical model obtained
from BIM geometry, thus providing better automation for
preparing FEM model. Program logic is explained and test
cases shown
Variational approach for resolving the flow of generalized Newtonian fluids in circular pipes and plane slits
In this paper, we use a generic and general variational method to obtain
solutions to the flow of generalized Newtonian fluids through circular pipes
and plane slits. The new method is not based on the use of the Euler-Lagrange
variational principle and hence it is totally independent of our previous
approach which is based on this principle. Instead, the method applies a very
generic and general optimization approach which can be justified by the
Dirichlet principle although this is not the only possible theoretical
justification. The results that were obtained from the new method using nine
types of fluid are in total agreement, within certain restrictions, with the
results obtained from the traditional methods of fluid mechanics as well as the
results obtained from the previous variational approach. In addition to being a
useful method in its own for resolving the flow field in circular pipes and
plane slits, the new variational method lends more support to the old
variational method as well as for the use of variational principles in general
to resolve the flow of generalized Newtonian fluids and obtain all the
quantities of the flow field which include shear stress, local viscosity, rate
of strain, speed profile and volumetric flow rate. The theoretical basis of the
new variational method, which rests on the use of the Dirichlet principle, also
provides theoretical support to the former variational method.Comment: 22 pages, 6 figures, 5 table
Design study of a regenerative pump using one-dimensional and three-dimensional numerical techniques
Regenerative pumps are low cost, compact, able to deliver high heads at low flow rates. Furthermore with stable performance characteristics they can operate with very small NPSH. The complexity of the flow field is a serious challenge for any kind of mathematical modelling. This paper compares an analytical and numerical technique of resolving the performance for a new regenerative pump design. The performance characteristics computed by a CFD approach and a new one-dimensional model are compared and matched to experimental test results. The approaches of both modelling techniques are assessed as potential design tools. The approaches are shown to not only successfully resolve the complex flow field within the pump; the CFD is also capable of resolving local flow properties to conduct further refinements. The flow field is represented by the CFD as it has never been before. A new design process is suggested. The new regenerative pump design is considered with a comparable duty centrifugal pump, proving that for many high head low flow rate applications the regenerative pump is a better choice
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Reduction of gear pair transmission error with tooth profile modification
The gear noise problem that widely occurs in power transmission systems is typically characterised by one or more high amplitude acoustic signals. The noise originates from the vibration of the gear pair system caused by transmission error excitation that arises from tooth profile errors, misalignment and tooth deflections. This paper aims to further research the effect of tooth profile modifications on the transmission error of gear pairs. A spur gear pair was modelled using finite elements, and the gear mesh was simulated and analysed under static conditions. The results obtained were used to study the effect of intentional tooth profile modifications on the transmission error of the gear pair. A detailed parametric study, involving development of an optimisation algorithm to design the tooth modifications, was performed to quantify the changes in the transmission error as a function of tooth profile modification parameters as compared to an unmodified gear pair baseline
Learning Singularity Avoidance
With the increase in complexity of robotic systems and the rise in non-expert
users, it can be assumed that task constraints are not explicitly known. In
tasks where avoiding singularity is critical to its success, this paper
provides an approach, especially for non-expert users, for the system to learn
the constraints contained in a set of demonstrations, such that they can be
used to optimise an autonomous controller to avoid singularity, without having
to explicitly know the task constraints. The proposed approach avoids
singularity, and thereby unpredictable behaviour when carrying out a task, by
maximising the learnt manipulability throughout the motion of the constrained
system, and is not limited to kinematic systems. Its benefits are demonstrated
through comparisons with other control policies which show that the constrained
manipulability of a system learnt through demonstration can be used to avoid
singularities in cases where these other policies would fail. In the absence of
the systems manipulability subject to a tasks constraints, the proposed
approach can be used instead to infer these with results showing errors less
than 10^-5 in 3DOF simulated systems as well as 10^-2 using a 7DOF real world
robotic system
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