In SharePoint 2010 we have completely removed the UI for resetting the disk based BLOB cache. This means that you can only reset it through the SharePoint Object Model . Fortunately, since we invested in the SharePoint 2010 Management Shell, it's not that difficult to do. Here is some sample code to help you do this:

# A script to reset the SharePoint 2010 Disk Based Cache for BLOBs
# Example: .\Reset-Blob-Cache.ps1 http://MySiteCollection

# Loads the SharePoint 2010 PowerShell extensions so we can easily
# get a reference to our dlls.
try
{
    if(((Get-PSSnapin | foreach {$_.Name}) -contains "Microsoft.SharePoint.PowerShell") -eq $false)
    {
      Add-PSSnapIn Microsoft.SharePoint.PowerShell -ErrorAction Stop
    }
}
catch
{
    Write-Host -ForegroundColor "red" "This script only works on machines with SharePoint 2010 installed.`n"
    Exit
}

# Use Reflection to get a reference to our dlls.
try
{
    $spAssembly = [System.Reflection.Assembly]::GetAssembly([Microsoft.SharePoint.SPSite])
    [System.Reflection.Assembly]::Load($spAssembly) | Out-Null
}
catch
{
    Write-Host -ForegroundColor "red" "Could not locate the SharePoint Assemblies.`n"
    Exit
}

# You must provide a site upon which to execute the cache reset.
if ($args.length -ne 1)
{
    Write-Host "Expected 1 arguments:"
    Write-Host "<site_url>"
    exit
}

$site_url = $args[0]

try
{
    $site = Get-SPSite -Identity $site_url -ErrorAction Stop
}
catch
{
    Write-Host -ForeGround 'Red' "$_"
    Write-Host -ForeGround 'Red' "Please correct the arguments and try again.`n`n"
    Exit
}

$warning = "This will clear the blob cache for all sites in this application, on all WFEs in the farm. `nPress 'y' to continue:"

Write-Host -ForeGround 'Yellow' -noNewLine $warning

$key = $host.UI.RawUI.ReadKey("NoEcho,IncludeKeyUp")

if ($key.Character -ine "y")
{
    Write-Host "`nYou chose not to flush the cache."
    exit
}

Write-Host "`nFlushing..."
[Microsoft.SharePoint.Publishing.PublishingCache]::FlushBlobCache($site.WebApplication)

Write-Host "Flushed Cache for:" $site.WebApplication.Name