Posts Tagged ‘Robert Warren’

Flow Simulation ‘Replicate Condition’

Thursday, March 20th, 2014

New for 2014 a user has the ability to apply a single Boundary Condition to multiple instances of the same part.  This is a great time saving tip.  No more manually adding the same Boundary Condition to instances of the a part.

With your setup you can assign Boundary Conditions such as an “Inlet”, “Outlet”, and “Heat Source” to  ”Part1 “(face/volume) for example.

Simply Right Mouse Button the Boundary Condition and select “Copy to Component Instance”.

The Boundary Condition auto populates on all “Part 1s” in the model.

You can deselect the instance(s) you do not want included.

Note: the “Part 1″ needs to be a part in an assembly for the transfer to work.

For the full pdf instructions please see the link below:

Replicate Condition Flow

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Circuit Works and Flow Simulation Working Together

Tuesday, February 25th, 2014

When you think about it, it makes sense that different parts of our SolidWorks Software work together to make a total package.  Keeping in this tradition now in 2014 Circuit Works and Flow Simulation work together to make your life easier.

2014 Flow simulation now imports the Circuit Works component properties and applies them automatically as boundary conditions in your Flow Simulation setup.  Previously these properties would be input manually.  Now we can import ECAD file PCB or Component Thermal Properties to Flow Simulation.

Circuit Board

Circuit Board

Some of the properties that can be directly utilized from Circuit Works are, Dielectric and Conductor Density, Specific Heat, Conductivity for PCBs, and Conductivity for Volumetric Heat Sources.

Circuit Board Thermal Flow

Circuit Board Thermal Flow

Two Import Options:

Right-click Heat Sources and select Import volume source from model. Select the heat sources to import in Item properties.
Right-click Printed Circuit Boards and select Import Printed Circuit Boards from model. Select the PCBs to import in Item properties.

Import Interface

Import Interface

If you are doing Flow Simulation on Electronics Enclosures check out the new Circuit Works import options.  This new feature is a great time saver.  Manually adding these properties on a typical circuit board (100′s of components) is tedious and time consuming.  Circuit Works integration brings this task down to a few simple clicks.

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

What Can’t You Design In SolidWorks? #3

Tuesday, January 28th, 2014

RC Hovercraft #3 – SolidWorks Simulation

To review, I had 4 main design criteria for the Remote Control Hover Craft.

  • Utilize the SolidWorks and SolidWorks Simulation Suite of software to develop and optimize the hovercraft design.
  • The RC Hovercraft’s main components will be 3D Printed using the Stratasys UPrint.
  • Easy to Assemble. I want to make the assembly as easy and as straight forward as possible with concise instructions.
  • For purchased components, use low cost, off the shelf components including the electric motors, electronic speed control (ESC), batteries, and propellers.

The next step of the design process is to verify using  SolidWorks Flow Simulation  that the motor and propeller combination will provide a proper amount of air flow to lift the hover craft.

Flow Simulation provides an understanding of  flow in an internal or external volume.  Flow Simulation calculates flow with media including Gases, Fluids, Real Gases, and Non Newtonian Fluids.  Flow Rate, Velocity, Pressure , Vortices, and many other parameters are calculated during the solution.

The following  calculation with the provided manufacturer information was used to calculate the flow parameter boundary conditions for the simulation.

CFM = Cubic Feet per Minute = Volumetric Flow Rate

Mass Flow Rate = (Density) x (Volumetric Flow Rate)

Newton’s Second Law of Motion:  Force = (Mass) x (Acceleration), or F = ma

F = ma = (Mass Flow Rate) x (Velocity), given a constant flow velocity

(i.e., constant propeller speed and pitch angle).

Velocity = (Volumetric Flow Rate) / (Area), where Area = (Pi) x (r^2), the

length of a propeller blade is a good approximation for the radius, r.

Thrust = (Density) x (CFM^2) / ((Pi) x (r^2))

Note: Keep track of your units!

The hover craft’s Flow Simulation was approached from an external analysis type.  A volume was specified around the  hover craft to capture flow into the  inlet and out of the bladder, and its effect from the surrounding environment.  A fan was used to provide the draw of air through the inlet into the internals of the hover craft.  Parts of the hover craft were removed including the canopy cover batteries, and escs.  These components are unnecessary for teh flow run and would increase computational time.

 

Air Velocity

Air Velocity

Air Velocity Top

Air Velocity Top

The results from the Flow Simulation run show a symmetric and even outlet pattern of flow from the Hover Craft’s “Bladder”.  The parameters provided by the flow simulation suggest that the motor and propeller combination should be sufficient for lifting the craft.

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Mesh Improvements For Simulation Flow

Monday, December 2nd, 2013

SolidWorks Flow 2014 has been released and there are several updates.  I want to talk about the Mesh Improvements inside of Flow Simulation.

Two Main Changes:

  • Mesh Parallelization
  • Local Initial Mesh Regions now Adaptive

 

Lets discuss the Mesh Parallelization first.  There are three stages during mesh generation in Flow Simulation  Geometry Evaluation, Mesh Capture, and Mesh Saving.

Flow Simulation in 2013 utilized one processor for all three mesh operations.  Flow Simulation 2014 utilizes multiple cores(user specified) for the Mesh Capture(resource intense) portion of the process.  This speeds up the mesh drastically between versions.  A 1.5 million cell model in 2013 took 23 minutes to mesh.  In 2014 the same computer, model, and mesh settings took 11 minutes. Over a 50% improvement for this example model.

 

Adaptive Meshing has always been available in Flow Simulation, however it was only effective on the entire computational domain.  Adaptive meshing is a setting that allows the software to automatically refine areas of high gradient in the flow, allowing the software to converge the results.  Adaptive meshing on a localized region is now available for 2014.  A localized region is a region that a user specifies to have manual mesh refinements on.  This is done by inserting a body in the flow region and specifying it as a local initial mesh.  This region can now be specified to be affected by adaptive meshing.  This speeds up convergence by localizing the adaptive changes.

 

Mesh

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

e Drawings Augmented Reality For IOS Mobile Devices

Wednesday, July 31st, 2013

Released for 2013 e Drawings is a new feature called Augmented Reality (AR). Being July already, this topic may not be new to many of you but I wanted to go over what AR is all about and a helpful trick I learned when utilizing it.

 

AR is a portion of e Drawings that allows a user to view their model in a real world setting.  AR utilizes the mobile devices rear facing camera and a QR code.  Simply place the QR print out on the ground or wall and point the mobile device towards the print.  The model is superimposed over the background image the camera is taking.  Zoom, Pan, Rotate, and scaling is all available when using AR.

Augmented Reality

The limitation I found is with the mobile devices camera. The QR code is only recognized up to about 5 feet away, after that the QR is not recognized.   This is limiting with large models that you would need to be farther than 5 feet away to properly scale in the room.  Because we cannot change the camera properties of the device lets change the QR code. To increase the range of recognition is simple,  enlarge the QR code.  I have found that this is fairly proportional.  a QR at 100% size is recognized at about 5 feet, a 200% sized QR code is recognizable up to 10 feet, and so on.

QR

Below are some links and additional information on this exciting technology.

 

https://itunes.apple.com/us/app/edrawings-pro/id553557031?ls=1&mt=8

 

http://www.youtube.com/watch?v=rVcIaBAQSE4

 

http://www.youtube.com/watch?v=_Ij9kcWsni4

 

 

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Configurations or Display States Preparing for Simulation

Monday, July 1st, 2013

Introduction:

Finite Element Analysis generally requires a model to be simplified of extraneous parts or features in order to analyze the model efficiently.  This is common practice among analysts, and is utilized in SolidWorks Simulation.  In this blog I am going to discuss the two main SolidWorks methods of simplifying a model and discuss the preferred method between configurations and display states.

 

Display States and Configurations:

Display State:

Display States allow a user to specify different hide show states, appearances, display modes, and transparencies, for a part or assembly.  Display states are accessed under the configurations tab in the feature manager tree.

Right-click in an open area of the Configuration Manager and click Add Display State. The new display state is added to the list of display states at the bottom of the tab. Define the new display state by clicking to show the Display Pane and make changes, or by making changes on screen.

Configurations:

Configurations allow a user to create multiple variations of a part or assembly within a single document.  To create a configuration, you specify a name and properties, then you modify the model to create the design variations you want.

  • In part documents, configurations allow you to create families of parts with different dimensions, features, and properties, including custom properties.
  • In assembly documents, configurations allow you to create:
    • simplified versions of the design by suppressing components.
    • families of assemblies with different configurations of the components, different parameters for assembly features, different dimensions, or configuration-specific custom properties.
  • In drawing documents, you can display views of the configurations you create in part and assembly documents.

You can create configurations using any of the following methods:

  • Create configurations manually.
  • Use design tables to create and manage configurations in a Microsoft Excel worksheet. You can display design tables in drawings.

I bring your attention to both the Configurations and Display States because both can be used to simplify a model however one method is preferred within SolidWorks.  Because the configurations use suppress and unsuppress to remove the part or feature from calculation, and not simply hide from view this is the preferred method.

In simulation when a part is hidden it is still seen as a mesh-able entity that requires a material definition, and is included in the analysis.  You can at this point exclude the part from analysis however doing this upfront through configurations and suppression is the easiest method.

 

Example:

The steering bracket and connecting parts in the suspension assembly below require analysis.  To leverage the existing assembly we will use the configuration method from above.

Switch to the Configuration Tab

Assembly

Right Mouse Button and Choose New Configuration

Add Config

Suppress by right mouse buttoning on the components not needed in the analysis, and choose suppress

Suppressed Parts

Start New Study

Only the Un-Suppressed Parts are available to analyze

Study

 

Sources: 2013 SolidWorks Help File

http://help.solidworks.com/2013/english/SolidWorks/sldworks/c_Configurations_Overview.htm?id=84a0a1600c6f4e77a4220606721035c6#Pg0

 

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

What Can’t You Design In SolidWorks? #2

Tuesday, April 2nd, 2013

RC Hovercraft #2 – SolidWorks

To review, I had 4 main design criteria for the Remote Control Hover Craft.

  • Utilize the SolidWorks and SolidWorks Simulation Suite of software to develop and optimize the hovercraft design.
  • The RC Hovercraft’s main components will be 3D Printed using the Stratasys UPrint.
  • Easy to Assemble. I want to make the assembly as easy and as straight forward as possible with concise instructions.
  • For purchases components, use low cost, off the shelf components including the electric motors, electronic speed control (ESC), batteries, and propellers.

I proceeded forward with the design of the Hovercraft using SolidWorks 3D mechanical design software.  SolidWorks allowed me to quickly develop and execute a first pass design, utilizing Multi-Body Parts, In context Assembly Modeling, Sketch Pictures, Fastening Features, Interference Detection, and several other standard options.  All of this came together in an initial design that meets the above criteria.

The design started with the Top Plate part that houses the downward facing fan assembly and gives the craft its overall dimensional size.  I kept the craft under the 8″ by 8″ tray size of the Stratasys UPrint 3D Printer.  The part consists of multi-bodies; one for the plate and the other for the fan housing.  These bodies have minimal tolerance so they are a snug fit when pressed together for final assembly.  This design criteria is so that if the propeller needs to be serviced later total dis-assembly of the craft does not have to take place. Simply pull the fan unit upward out of the top plate.

Top Plate

Top Plate

Exploded View Front

Exploded View Front

Exploded View Back

Exploded View Back

 

The chassis continues with a bottom plate and separating ribs.  The chassis is hollow as the air needs to fill this cavity before exiting out of the skirt.  The skirt is intended to be a bicycle inner tube cut to size with holes cut around the inner bottom portion allowing the air to escape.  The skirt will be held on by two fastening plates and standard hobby store machine screws.

Section View

Section View

The back cowling snaps into place with a Snap Hook.  The Fastening Feature command was used to create this geometry.  The Snap Hook will allow for ease of assembly, and the cowl contains a cross bar with built in motor mount sized for a 9V-11V brushed can motor. The Cowling and Top Plate will make up the mounting location for the dual rudder system.  The system is driven by  an S75 Nano servo available at most local hobby shops.

Cowl

Cowl

 

 

The canopy will cover all of the electronics including the Receiver, two Electronic Speed Controls (ESC), And two Li-Poly 300MAH 11.1V Batteries.  One ESC and battery per motor.  I originally set out utilizing the Sketch Picture and Surfacing to create the canopy structure. This worked out well, however at this time I did not have the electronics in the full assembly.  When trying to accommodate the electronics under the first variation of the canopy I visibly had interference. Luckily utilizing in-context editing and having a well planned design intent, the changes to the canopy allowed for an easy and quick change.

Sketch Picture

Sketch Picture

Interference Original Canopy

Interference Original Canopy

Receiver & ESCs

Receiver & ESCs

 

Batteries, Receiver, and ESCs

Batteries, Receiver, and ESCs

Canopy Design Change

Canopy Design Change

 

 

There is still much to do with the modeling aspect, but for now I have a good working start to the project and a starting point to investigate the flow and stress characteristics of the design.  The next step is to utilize Flow Simulation to verify the lift ability of the motor and propeller combination  for the lift fan and the rear facing fan assembly.

Top

Top

Front

Front

Back

Back

Side

Side

 

 

 

 

 

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

What Can’t You Design In SolidWorks?

Monday, February 25th, 2013

RC Hovercraft #1

For this blog series I wanted to design something from scratch.  Not necessarily a new idea but something fun and cool.  My intention is to design a Remote Control Hovercraft from the ground up.

I want to give you a brief description and history of a Hovercraft:

A hovercraft or air-cushion vehicle is a vehicle capable of travelling over variable surfaces, such as land and water.  The hovercraft operates by forcing a high pressure of air between the bottom of the craft and the surface below.  This high pressure of air lifts the vehicle upward essentially “hovering” above the ground on a cushion of air. The first practical design for hovercraft derived from several coinciding inventions in the 1950s to 1960s. They are now used throughout the world as specialized vehicles for transport and other applications.

500px-Hovercraft_-_scheme.svg

  1. Propulsion Propellers
  2.  Air
  3. Lifting Fan
  4. Flexible skirt

YouTube Preview Image

I have specific goals in mind that I want to meet in the design and build of this project.

 

Goals of the Hovercraft Design:

  • Utilize the SolidWorks and SolidWorks Simulation Suite of software to develop and optimize the hover craft design.
  • The RC Hovercraft’s main components will be 3D Printed using the Stratasys UPrint.
  • Easy to Assemble. I want to make the assembly as easy and as straight forward as possible with concise instructions.
  • For purchased components, use low cost, off the shelf components including the electric motors, electronic speed control (ESC), batteries, and propellers.

I am starting from just an idea, and a sketch. We will see where the design leads.

Hover Craft2

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

When To Use A Bearing Load

Friday, January 25th, 2013

The use of a bearing load is brought up frequently during training and technical support discussions. I want to elaborate on this topic with a simple example, illustrating when to use and when it is not necessary to use the bearing load.
Let’s step back a minute and talk about what a bearing load is. According to the SolidWorks Help file:

 

Bearing Loads


Bearing loads develop between contacting cylindrical faces or edges of shells.
In most cases, the contacting faces or edges have the same radius. The bearing forces generate a non-uniform pressure at the interface of contact. You can select between a sinusoidal variation and a parabolic variation in the appropriate half-space, as shown in the figure.

Bearing Load Distribution

In contrast, a uniform load does not vary in strength closer to the tangency of the tube. The load is constant across the applied face.
Setup:


We will examine two models and four scenarios in this exercise. The models will be both a solid and a hollow shaft. The shaft dimensions will be 14″ long with a 2″ diameter. Additionally, the hollow shaft will have a wall thickness of 0.125″.
Both the Solid and Hollow tubes were loaded with a distributed and bearing load in order to compare and contrast the results. Both models were held fixed at either end. The load was applied to the entire length of the top half of the shaft in a vertical direction.

Loading
The Results:


Between the distributed and bearing load on the Solid model, there is no difference in stress and displacement. On the hollow tube, the bearing load shows a drastic difference in the displacement compared to the uniform load. The bearing load shows the majority of the load is being focused on the center of the tube.
Model Load Stress Displacement

Model Load Stress Displacement
Solid 2000lb Distributed 3943.6 psi 0.001066 in.
Solid 2000lb Bearing 3943.4 psi 0.001065 in
Hollow 2000lb Distributed 11,534.6 psi 0.003009 in.
Hollow 2000lb Bearing 12,084.9 psi 0.003467 in.

Significant digits are for illustration only.

The stress is 4.5% higher in the ‘hollow shaft – bearing load’ combination as compared to the ‘hollow shaft – distributed load’ example.
Load Solid Stress
Stress Above Displacement Below Solid Distributed Load
Load Solid Disp

Bearing Load Solid Stress

 

Stress Above Displacement Below Solid Bearing Load

Bearing Load Solid Disp

 

Load Hollow Stress

 

Stress Above Displacement Below Hollow Distributed Load

 

Load Hollow Disp

 

 
Bearing Load Hollow Stress

Stress Above Displacement Below Hollow Bearing Load

Bearing Load Hollow Disp
Summary:


In summary, the bearing load should be utilized when dealing with a hollow or thin walled, cylindrical geometry. Utilizing solid geometry the load differences do not affect the results. The solid geometry distributes the load throughout the solid volume and is inherently stiffer. The hollow tube, missing its internal mass, shows a difference in the displacement of the applied load. The uniform load displaced evenly from tangent edge to tangent edge where as the bearing load concentrated in the center.

A bearing load can be applied to solid and hollow cylindrical geometry however it is only necessary for hollow or thin geometry.

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Flow Simulation and the 75 Dollar Question

Friday, June 22nd, 2012

Is it worth the extra 75 dollars for a long tube header versus a short tube?

Let’s start answering this by examining how an exhaust header works, and why you would want one.  Headers are one of the easiest bolt-on accessories you can use to improve an engine’s performance. The goal of headers is to make it easier for the engine to push exhaust gases out of the cylinders.

 

To further understand why the exhaust manifold has an impact on performance let’s review the  combustion cycle of a gasoline engine.

  1. The intake stroke-  Starts with the piston at the top of the cylinder.  As the piston moves downward the intake valve opens allowing the air fuel mixture to enter the cylinder.
  2. The compression stroke-  Moves the piston back up to compress this air fuel mixture, causing the ignition of the air fuel mixture to be more powerful.
  3. The combustion stroke –  When the piston reaches the top of the cylinder, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down.
  4. The exhaust stroke- Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the header.

During the exhaust stroke, back pressure robs the engine of power. The exhaust valves open at the beginning of the exhaust stroke, and then the piston pushes the exhaust gases out of the cylinder. The more resistance there is to the piston expelling the exhaust gases, the greater the power loss.

Once the exhaust gases exit the cylinder they end up in the exhaust manifold. In a four-cylinder engine, all cylinders utilize the same manifold. From the manifold, the exhaust gases flow into one pipe toward the catalytic converter and the ­muffler. The idea behind an exhaust header is to eliminate the manifold’s back pressure. Instead of a common manifold that all of the cylinders share, each cylinder gets its own exhaust pipe. Old hot-rodder intuition, gut feel, and experimentation lead to each pipe being the same length, and using a two into one set up. Two into one specifies that the pipe leading from two cylinders merge into one.  In the case of a four cylinder, pipes from cylinders 1 and 2 lead to one pipe, and pipes from cylinders 3 and 4 lead to one pipe.  Those two pipes then merge again into the collector. The two into one method “smoothes” the flow through the pipe causing less turbulence when the flow fields merge.  These pipes come together in a larger pipe called the collector. By making them the same length, it guarantees that each cylinder’s exhaust gases arrive in the collector spaced out equally so there is no back pressure generated by the cylinders sharing the collector. Basically Header=Power, and we all want more power.

The 75 dollar question arose from my sister.  She is considering replacing her stock exhaust manifold with an after-market header, and was wondering what was the best “bang for the buck”.  After researching the topic extensively we found that across all the after-market brands the designs seemed to be the same regarding pipe routing, materials, etc.  So the main question came down to should she buy the “short tube” or “long tube” header?

Both the “long tube” and “short tube” headers have equal length pipes from the engine block to the collector.  Both ran a two into one method.  The long tube header however claims that since it is longer by design there would be less back pressure due to a smoother flow.  The differentiator was about 75 dollars, and the fact that the “long tube” header would need the catalytic converter to be moved and remounted by a muffler shop.  The “short tube” header is a direct bolt in.

I couldn’t resist turning to Flow Simulation to solve this question.

We purchased the long and short tube headers, and removed the stock manifold to be able to accurately take measurements from them.  The models are close but not exact without a reverse engineering tool such as a scanner or arm.

After the models were completed the next step became the boundary conditions.  I was able to find a good reference guide located on line from www.donaldsonexhaust.com.  Given the engine Horsepower, cubic inch displacement, and operating RPM I was able to determine Intake airflow, and exhaust gas flow in CFM.

This calculated the exhaust gas CFM to be 520.00 CFM, or 130.0 CFM per port. Please see the hand calculations below.

Yes Engineers Still Do Hand Calcs

Knowing the CFM of the exhaust leaving the cylinder allows us to compare pressure drop from the inlet to outlet across the three manifold models.  The stock exhaust will be the base line for comparison.

 

Model Set Up:

 

Inlet Condition:                130 CFM per inlet port

Outlet Condition:             Environmental Pressure

Surface Goals:                   Each Inlet Goal – Static Pressure / Mass Flow Rate

Outlet Goal – Static Pressure / Mass Flow Rate

Results:


Stock Flow Path

Stock Pressure Gradient

Short Tube Pressure Gradient

Short Tube Flow Trajectories

Long Tube Pressure Gradient

 

Summary:

 

The “short tube” header is hands down the best value.  Both after-market headers showed a drastic decrease in pressure drop over the stock manifold however, the “long tube” header only had an edge over the “short tube” pressure by 0.019 PSI.  As a bonus the “short tube is a direct bolt in, not requiring the existing catalytic converter to be moved.  As Engineers we are always worried about time and money, and are often faced with a decision regarding these two factors.  From my engineering background and proof provided by flow I recommended the “short tube” header.

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

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